Showing papers by "Mines ParisTech published in 2002"
TL;DR: In the making process of an innovation, it is easy to retrospectively explain success as a stroke of genius or failure as a blatant mistake as discussed by the authors, but what about innovation in the making? How does the innovator navigate the pitfalls which threaten him?
Abstract: We all know of innovations which either made their creators a fortune or which led to their downfall. It is easy to retrospectively explain success as a stroke of genius or failure as a blatant mistake. Easy in retrospect…but what about innovation in the making? How does the innovator navigate the pitfalls which threaten him?
533 citations
TL;DR: The biosorption of three commonly used reactive dyes, from aqueous solutions by oven-dried Rhizopus arrhizus biomass was studied in a batch system with respect to pH, initial dye concentration and initial metal ion concentration.
314 citations
TL;DR: “Solve the technical problems first”, “then the authors’ll deal with the market”; the real history of innovations does not generally follow this simple schema.
Abstract: “Solve the technical problems first”, we often hear, “then we’ll deal with the market”. The real history of innovations does not generally follow this simple schema; it is made of adaptations, series of trial and error and countless negotiations between numerous social actors. A genuine combat from which conquerors who know how to choose good representatives emerge.
274 citations
TL;DR: In this paper, the authors developed a micro-mechanical framework for the whole coalescence regime, which is defined by a set of constitutive equations including a closed form of the yield surface along with appropriate evolution laws for void shape and ligament size.
Abstract: Significant progress has been recently made in modelling the onset of void coalescence by internal necking in ductile materials The aim of this paper is to develop a micro-mechanical framework for the whole coalescence regime, suitable for finite-element implementation The model is defined by a set of constitutive equations including a closed form of the yield surface along with appropriate evolution laws for void shape and ligament size Normality is still obeyed during coalescence The derivation of the evolution laws is carefully guided by coalescence phenomenology inferred from micromechanical unit-cell calculations The major implication of the model is that the stress carrying capacity of the elementary volume vanishes as a natural outcome of ligament size reduction Moreover, the drop in the macroscopic stress accompanying coalescence can be quantified for many initial microstructures provided that the microstructure state is known at incipient coalescence The second part of the paper addresses a more practical issue, that is the prediction of the acceleration rate δ in the Tvergaard–Needleman phenomenological approach to coalescence For that purpose, a Gurson-like model including void shape effects is used Results are presented and discussed in the limiting case of a non-hardening material for different initial microstructures and various stress states Predicted values of δ are extremely sensitive to stress triaxiality and initial spacing ratio The effect of initial porosity is significant at low triaxiality whereas the effect of initial void shape is emphasized at high triaxiality
274 citations
TL;DR: In this article, the authors used a video-controlled testing system to determine the evolution of volume strain in polyethylene terephtalate (PET) and high-impact polystyrene (HIPS) by measuring in real time the three principal strain components in a small volume element, while the specimens are deformed under uniaxial tension at constant true strain rate.
273 citations
TL;DR: In this article, a study of cooling crystallization of a potassium sulphate solution in a batch reactor is described, where the effect of ultrasound on primary nucleation was investigated by measures of induction time and metastable zone width of unseeded solutions.
221 citations
TL;DR: The objective is to perform a likelihood control of the data and to check their plausibility, achieved by comparing observations with some expectations based upon the extraterrestrial irradiation and a simulation of the irradiation for clear skies.
190 citations
TL;DR: In this article, photo-degradation and biodegradability have been studied for three different families of non-biodegradable textile dyes (Intracron reactive dyes, Direct dyes and Nylanthrene acid dyes) using VUV photolysis.
Abstract: Photo-degradation and biodegradability have been studied for three different families of non-biodegradable textile dyes (Intracron reactive dyes, Direct dyes and Nylanthrene acid dyes) and a textile wastewater, using VUV photolysis. Ninety percent of color removal of dye solutions and wastewater is achieved within 7 min of irradiation. Biological oxygen demand (BOD) was found to increase during discoloration process while chemical oxygen demand (COD) decreased. The biodegradability index (BOD5/COD) increases up to 0.40 for most of the dye solutions when total discoloration is obtained. It implies that VUV photolysis tends to enhance the biodegradability of dye containing solutions. Thus, this technique could be used as a pre-treatment step for conventional biological wastewater treatment.
189 citations
TL;DR: In this article, a comparison of sorption isotherms and sorption kinetics of chitosan derivatives with those of glutaraldehyde cross-linked chitosa is made.
Abstract: Palladium is efficiently extracted from dilute acidic solutions using chitosan derivatives. Sorption performances are enhanced by modification of chitosan through the grafting of sulfur compounds (thiourea, rubeanic acid), which creates new chelating groups, on chitosan backbone using glutaraldehyde as a linker. A comparison of sorption isotherms and sorption kinetics of these two derivatives with those of glutaraldehyde cross-linked chitosan shows that the rubeanic acid derivative of chitosan is the more efficient for the uptake of palladium from dilute solutions. The chemical modification is suspected of bringing chelating functionalities to the ion exchange resin. Sorption capacity is not influenced by the particle size of rubeanic acid derivative of chitosan. Sorption isotherms are described by the Langmuir equation. Increasing the temperature of the solution has little effect on sorption performances. Sorption kinetics are not greatly influenced by the particle size of the sorbent.
161 citations
TL;DR: Modified chitosan gel beads, which had been prepared by the molybdate adsorption and coagulation methods, were tested for As(III) and As(V) removal from dilute solutions and the process appears to be directed to the treatment of industrial effluents or as a pre-concentration process.
155 citations
TL;DR: In this paper, the growth kinetics of coarse intragranular precipitates were investigated during the cooling of an aluminium alloy AA 7010 from the solutionizing temperature, where interrupted quenching was performed at various temperatures and different holding times.
TL;DR: In this paper, a stereo correlation-based stereo-vision technique was used to measure the 3D shape of a stamped sheet metal part or the surface strain field undergone by the part during the stamping process.
TL;DR: In this paper, a model based on the elastic-plastic theory and a yield function is used to limit the admissible stresses in a tablet during a compaction cycle, which depends on the first and second invariants of the stress tensor: pressure and stress deviation.
TL;DR: In this article, a two-point calibration procedure was proposed for continuous glucose monitoring, where one point calibration was performed before each meal, and the other was performed after each meal.
TL;DR: In this article, a self-consistent model was applied to predict the plastic flow behavior during hot working of alpha/beta titanium alloys with wrought (equiaxed alpha) microstructures as a function of flow behavior and volume fractions of the individual phases.
Abstract: A self-consistent model was applied to predict the plastic flow behavior during hot working of alpha/beta titanium alloys with wrought (equiaxed alpha) microstructures as a function of the flow behavior and volume fractions of the individual phases. For this purpose, constitutive relations that incorporated composition-dependent strength coefficients were determined for the alpha and beta phases. With these constitutive relations and measurements of the specific compositions and volume fractions of the two phases at hot-working temperatures, the flow stress dependence on temperature under nominally isothermal conditions and the (average) strain rates in the individual phases were predicted for Ti-6Al-4V. The effect of temperature transients during hot deformation on the flow stress under nonisothermal (conventional) forging conditions and under nominally isothermal, high strain-rate conditions was also established using the self-consistent modeling approach. In these instances, the effect of a rapid temperature drop or rise, respectively, on the retention of a metastable microstructure was quantified. The predicted flow behaviors showed good agreement with experimental measurements.
TL;DR: In this paper, a numerical simulation method for the coupling between stress and hydrogen diffusion is proposed, based on the diffusion equation including a hydrostatic stress gradient term, and on a discretisation of the hydrogen concentration field.
TL;DR: In this paper, a new method based on migration velocity analysis (MVA) is proposed to estimate 2D velocity models from seismic reflection data with no assumption on reflector geometry or the background velocity field.
Abstract: We present a new method based on migration velocity analysis (MVA) to estimate 2‐D velocity models from seismic reflection data with no assumption on reflector geometry or the background velocity field. Classical approaches using picking on common image gathers (CIGs) must consider continuous events over the whole panel. This interpretive step may be difficult—particularly for applications on real data sets. We propose to overcome the limiting factor by considering locally coherent events. A locally coherent event can be defined whenever the imaged reflectivity locally shows lateral coherency at some location in the image cube.In the prestack depth‐migrated volume obtained for an a priori velocity model, locally coherent events are picked automatically, without interpretation, and are characterized by their positions and slopes (tangent to the event). Even a single locally coherent event has information on the unknown velocity model, carried by the value of the slope measured in the CIG. The velocity is e...
TL;DR: For irrotational flows, a new variational formulation of Saint-Venant equations is proposed that provides a simple method to establish the equations when the tank is moving and provide a simple and flatness-based algorithm for computing the steering open-loop control.
Abstract: We consider a tank containing a fluid. The tank is subjected to directly controlled translations and rotations. The fluid motion is described by linearized wave equations under shallow water approximations. For irrotational flows, a new variational formulation of Saint-Venant equations is proposed. This provides a simple method to establish the equations when the tank is moving. Several control configurations are studied: one and two horizontal dimensions; tank geometries (straight and nonstraight bottom, rectangular and circular shapes), tank motions (horizontal translations with and without rotations). For each configuration, we prove that the linear approximation is steady-state controllable and provide a simple and flatness-based algorithm for computing the steering open-loop control. These algorithms rely on operational calculus. They lead to second order equations in space variables whose fundamental solutions define delay operators corresponding to convolutions with compact support kernels. For each configuration, several controllability open-problems are proposed and motivated.
TL;DR: Fade is a vehicle detection and tracking system featuring monocular color vision and radar data fusion and generates a belief network organized in three layers: sources, position proposals, and correlation between proposals.
Abstract: This paper presents Fade, a vehicle detection and tracking system featuring monocular color vision and radar data fusion. Its main originality resides in its low-level fusion system. At each step and for each target, the fusion system fuses the results of four different image processing algorithms and radar information by automatically combining 12 different features and generating many possible target position proposals. It generates a belief network organized in three layers: sources, position proposals, and correlation between proposals. An inference algorithm is then used to find out the actual position of the target, by deducing which observations are wrong. The overall system runs in real time and has been evaluated on a variety of scenarios recorded in a real car using /sup RT/Maps. Fade yields very good detection results in most cases.
TL;DR: In this paper, the microstructure of an injection molding propylene copolymer is varied through systematic changes on the processing conditions (melt and mould temperatures and injection flow rate).
TL;DR: In this article, a two-point calibration procedure consists of the determination of a sensor sensitivity S and of a background current I(o) by plotting two values of the sensor signal versus the concomitant blood glucose concentrations.
TL;DR: In this paper, a new route in which the cracking operation is carried out in the absence of oxygen thanks to an external electric energy supply given by a plasma arc was presented, and the resulting carbon black is produced by incomplete combustion processes.
Proceedings Article•
01 Jan 2002TL;DR: This approach is validated by showing a consistent increase in performance when a state-of-the-art classifier uses the vector of features instead of the original expression profile to predict the functional class of a gene.
Abstract: We present an algorithm to extract features from high-dimensional gene expression profiles, based on the knowledge of a graph which links together genes known to participate to successive reactions in metabolic pathways. Motivated by the intuition that biologically relevant features are likely to exhibit smoothness with respect to the graph topology, the algorithm involves encoding the graph and the set of expression profiles into kernel functions, and performing a generalized form of canonical correlation analysis in the corresponding reproducible kernel Hilbert spaces.
Function prediction experiments for the genes of the yeast S. Cerevisiae validate this approach by showing a consistent increase in performance when a state-of-the-art classifier uses the vector of features instead of the original expression profile to predict the functional class of a gene.
TL;DR: In this paper, a generalized homogeneous substitution medium is used to replace a classical composite material by Cosserat and micromorphic equivalent ones at the global level when the structure made of a composite material is subjected to strong variations of the mean fields or when the intrinsic lengths of non-classical constituents are comparable to the wavelength of variation of mean fields.
Abstract: The need for generalized continua arises in several areas of the mechanics of heterogeneous materials, especially in homogenization theory. A generalized homogeneous substitution medium is necessary at the global level when the structure made of a composite material is subjected to strong variations of the mean fields or when the intrinsic lengths of non-classical constituents are comparable to the wavelength of variation of the mean fields. In the present work, a systematic method based on polynomial expansions is used to replace a classical composite material by Cosserat and micromorphic equivalent ones. In a second part, a mixture of micromorphic constituents is homogenized using the multiscale asymptotic method. The resulting macroscopic medium is shown to be a Cauchy, Cosserat, microstrain or a full micromorphic continuum, depending on the hierarchy of the characteristic lengths of the problem. .
TL;DR: It is shown that alkali chlorides can be extracted efficiently in an aqueous extraction step combining a calcium phosphate gel precipitation, and fly ash spiked with copper ions and treated by this process shows improved stability of metal ions.
TL;DR: In this paper, an experimental set up specially designed for the investigation of drying kinetics, of heat transfer coefficient evolution, and of the mechanical torque necessary for stirring was presented, which was applied to municipal sewage sludge.
Abstract: Whereas indirect agitated drying has been extensively studied for granular materials, little is known in the case of pasty products. We describe an experimental set up specially designed for the investigation of drying kinetics, of heat transfer coefficient evolution, and of the mechanical torque necessary for stirring. This device was applied to municipal sewage sludge. Preliminary experiments were performed to investigate the influence of ageing of sludge on the drying kinetics. It appears that ageing does have no effect except for the first two days. The influences of the wall temperature, the stirrer speed, the dryer load and the location of the stirrer against the heated wall were studied. Three different rheological behaviors were observed during sludge drying. In particular, the sludge goes through a “glue” phase, and high levels of mechanical strain are recorded when the compact mass begins to break up. A critical stirrer speed is found within the range 40–60 rpm. To shorten the drying ti...
TL;DR: In this paper, the potential of chitosan biopolymer for catalytic applications was investigated, and a chitosa-based catalytic catalyst was proposed for palladium-based applications.
Abstract: Owing to its high sorption capacity for precious metals (especially palladium), the potential of the chitosan biopolymer for catalytic applications was investigated. The catalyst was prepared in tw...
TL;DR: In this paper, a constitutive modelling deduced from a model proposed by Bouaziz and Guelton integrates this typical organisation of microtwins is integrated, and twinning is quantified by the partial volume fraction of twins in each system.
Abstract: The TEM study of our steel with a high manganese content reveals that mechanical twining (TWIP effect) occurs during the deformation at room temperature. Microtwins are organised into parallel stacks and two systems are sequentially activated in each grain. They participate to the deformation and they are strong obstacles for the dislocations and for other twins, leading to the decrease of the effective grain size. Thus, TWIP provides our alloy a very good ductility and a high hardening rate. Our constitutive modelling deduced from a model proposed by Bouaziz and Guelton [4] integrates this typical organisation of microtwins. Twinning is quantified in each grain by the partial volume fraction of twins in each system. A nucleation law for the microtwins is introduced which depends on the local stress and the stress relaxation due to pre-existing twins. The flow stress is deduced from the dislocation density, which evolves with the dynamical recovery and the decrease of the mean free path (MFP). The MFP takes into account the grain and twin boundaries and the forest dislocations. The strain is calculated by adding the contributions of dislocation glide and twinning accounting the orientation of the grain. To treat the polycristal, the behaviours of different grain orientations are mixed by assuming at each strain step that the increment of elastic energy stored is the same in each grain. The model was successfully applied to describe the mechanical properties of our alloy, for two different grain sizes. Some microstructural parameters are yet fitted. This leads to an insufficient prediction of the evolution of the microstructure. In further developments, we expect to introduce numerical simulation results on local characteristics of microtwins (thickness, critical resolved shear stress for twinning) and experimental results on the rate of twin nucleation.
TL;DR: In this article, the effect of coalescence on shear band development and associated fracture mode in plane strain is analyzed numerically using a recent elastic-viscoplastic Gurson-like model that accounts for void shape evolution, coalescence and post-coalescence micromechanics along with isotropic hardening and orthotropic plasticity.
Abstract: The macroscopic fracture in plane strain is known to be shear-like in ductile materials. In most structural materials, fracture starts after diffuse necking, at the centre of the specimen, by micro-void coalescence giving rise afterwards to the macroscopic shear fracture mode. In this paper, the effect of coalescence on shear band development and on associated fracture mode in plane strain is analysed numerically. The calculations are performed using a recent elastic-viscoplastic Gurson-like model that accounts for void shape evolution, coalescence and post-coalescence micromechanics along with isotropic hardening and orthotropic plasticity for the matrix behaviour. The latter is introduced to represent the actual flow properties of hot-worked materials. No kinematic hardening or nucleation formulation is used in order to focus attention on coalescence effects and to discuss, with respect to experiments, published results based on kinematic hardening and nucleation effects. The most important finding is the synergistic effect of plastic anisotropy and post-coalescence yield surface curvature upon the onset of a shear band after the fracture sets in at the centre of the specimen.
TL;DR: In this paper, an amorphous gas atomized powder was consolidated by warm extrusion and the onsets of the glass transition and crystallization temperatures of this extruded material were observed at slightly higher and lower temperatures than those of the starting powders.
Abstract: Cu47Ti34Zr11Ni8 amorphous gas atomized powders were consolidated by warm extrusion. After consolidation near 723 K using an extrusion ratio of 5, the material retains between 88% and 98% of the amorphous structure found in the gas atomized powder. The onsets of the glass transition and crystallization temperatures of this extruded material are observed respectively at slightly higher and lower temperatures than those of the starting powders. These temperature shifts are attributed to a composition change in the remaining amorphous phase during partial devitrification throughout the extrusion process. Powders extruded at the same temperature, but using higher extrusion ratios of 9 and 13, exhibit substantial devitrification during the consolidation process yet still deform homogeneously.