Showing papers by "Mines ParisTech published in 1993"
TL;DR: This glucose monitoring system, based on subcutaneous sensing of glucose, is able to provide a direct on line estimation of blood glucose concentration, using a novel calibration procedure and a monitoring unit designed for this purpose.
Abstract: We have developed a miniaturized glucose sensor which has been shown previously to function adequately when implanted in the subcutaneous tissue of rats and dogs. Following a glucose load, the sensor output increases, making it possible to calculate a sensitivity coefficient to glucose in vivo, and an extrapolated background current in the absence of glucose. These parameters are used for estimating at any time the apparent subcutaneous glucose concentration from the current. In the previous studies, this calibration was performed a posteriori, on the basis of the retrospective analysis of the changes in blood glucose and in the current generated by the sensor. However, for clinical application of the system, an on line estimation of glucose concentration would be necessary. Thus, this study was undertaken in order to assess the possibility of calibrating the sensor in real time, using a novel calibration procedure and a monitoring unit which was specifically designed for this purpose. This electronic device is able to measure, to filter and to store the current. During an oral glucose challenge, when a stable current is reached, it is possible to feed the unit with two different values of blood glucose and their corresponding times. The unit calculates the in vivo parameters, transforms every single value of current into an estimation of the glucose concentration, and then displays this estimation. In this study, 11 sensors were investigated of which two did not respond to glucose. In the other nine trials, the volunteers were asked to record every 30 s what appeared on the display during the secondary decrease in blood glucose. The results were analysed by comparing these readings (approximately 220 measurements per trial) to the changes in plasma glucose, measured every 15 min. The Error Grid Analysis indicated that 84.1±3.6% of the measurements were in zone A (accurate) and 15±3.6% were in zone B (acceptable). Considering each individual trial, the differences between the displayed value and the concomitant plasma glucose concentration ranged between −1.7 and 0.69 mmol/l. These excellent results were due to the absence of any significant lag between the changes in plasma glucose concentration and the changes in the result on the display. We conclude that this glucose monitoring system, based on subcutaneous sensing of glucose, is able to provide a direct on line estimation of blood glucose concentration.
361 citations
01 Jan 1993
TL;DR: This paper studies precise and efficient chaotic iteration strategies for computing fixed points of continuous functions over complete lattices of program properties when lattices are of infinite height and speedup techniques have to be used.
Abstract: interpretation is a formal method that enables the static and automatic determination of run-time properties of programs. This method uses a characterization of program invariants as least and greatest fixed points of continuous functions over complete lattices of program properties. In this paper, we study precise and efficient chaotic iteration strategies for computing such fixed points when lattices are of infinite height and speedup techniques, known as widening and narrowing, have to be used. These strategies are based on a weak topological ordering of the dependency graph of the system of semantic equations associated with the program and minimize the loss in precision due to the use of widening operators. We discuss complexity and implementation issues and give precise upper bounds on the complexity of the intraprocedural and interprocedural abstract interpretation of higher-order programs based on the structure of their control flow graph.
288 citations
15 Dec 1993
TL;DR: A solution of the motion planning without obstacles for the standard a-trailer system is proposed, which relies basically on the fact that the system is flat with the Cartesian coordinates of the last trailer as a linearizing output.
Abstract: A solution of the motion planning without obstacles for the standard a-trailer system is proposed This solution relies basically on the fact that the system is flat with the Cartesian coordinates of the last trailer as a linearizing output The Frenet formulae are used to simplify the calculations and permit to deal with angle constraints The general 1-trailer system, where the trailer is not directly hitched to the car at the center of the rear axle, is also flat The geometric construction used for the standard 1-trailer system can be extended to this more realistic system MATLAB simulations illustrate this method >
266 citations
TL;DR: In this paper, the authors consider the subclass of set systems which admit a global normal form where only the output and not its time derivatives appear in the nonlinearities and prove that, when the inverse dynamics are "input-to-state stable" (ISS) and a finite gain condition is satisfied, global asymptotic stability can be achieved by dynamic output feedback.
255 citations
23 Jun 1993
TL;DR: In this paper, the concept of connected operators was introduced in the context of mathematical morphology and it was shown that, from any connected operator acting on sets, one can construct a connected operator for functions.
Abstract: This paper deals with the notion of connected operators in the context of mathematical morphology. In the case of gray level functions, the flat zones over a space E are defined as the largest connected components of E on which the function is constant (a flat zone may be reduced to a single point). Hence, the flat zones of every function make a partition of the space. A connected operator acting on a function is a mapping which enlarges the partition of the space created by the flat zones of the functions. In this paper, it is shown that, from any connected operator acting on sets, one can construct a connected operator for functions. Then, the concept of pyramid is introduced and one of the most important results of this study is that, if a pyramid is based on connected operators, the flat zones of the functions increase with the level of the pyramid. In other words, the flat zones are nested. Then, a very important class of connected filter called `filter by reconstruction' is defined and its properties are stated and discussed. Rules to create pyramids relying on filters by reconstruction are proposed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
190 citations
TL;DR: A new (N + 1)-bucket algorithm is proposed for phase-stepping systems that eliminates most of the errors caused by the phase-shifter miscalibration.
Abstract: A new (N + 1)-bucket algorithm is proposed for phase-stepping systems. It eliminates most of the errors caused by the phase-shifter miscalibration.
188 citations
TL;DR: Based on a multifractal structure hypothesis for temporal rainfall processes, a general formula relating maximum possible point rainfall accumulations was derived as a function of the duration and sample size in this paper.
Abstract: Based on a multifractal structure hypothesis for temporal rainfall processes, a general formula relating maximum possible point rainfall accumulations is derived as a function of the duration and sample size. This formula appears to be in agreement with empirical observations. Such a result may reconcile some opposite points of view regarding extreme rainfall events, and suggests new ways of exploiting the scaling properties of rain processes.
164 citations
TL;DR: In this article, the effect of porosity, hardness, and thickness on the friction resistance of quasicrystalline coatings was investigated. And the authors found that the damage of the coatings is essentially brittle though some ductile behavior is observed.
Abstract: Coatings of three different compositions (Al65Cu20Fe15, Al64Cu18Fe8Cr8, and Al67Cu9Fe10.5Cr10.5Si3) were realized by various thermal deposition techniques. They were studied in the as-deposited state and after annealing. In view of potential applications, these quasicrystalline coatings were examined from the point of view of tribology: friction and wear. Some basic components of friction such as roughness, plowing, and adhesion have been studied in scratch testing. The friction resistance of the coating is strongly dependent on its inherent porosity, hardness, and thickness. The damage of the coatings is essentially brittle though some ductile behavior is observed. Static indentation hardness is in the range 500–600 HV0.03 (5–6 GPa), whereas the scratch hardness varies from 1.4 to 2.4 GPa depending on the percentage of porosity. Friction coefficients (measured at constant load of 20 N) were found to be typically 0.07 and 0.20 for diamond (tip radius R = 0.79 mm) and AISI 52100 (radius R = 0.79 mm) indenters, respectively.
153 citations
30 May 1993-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the nucleation of dislocation loops at crack tips and the development of the plastic zone were studied in single-crystal silicon samples precracked at room temperature and loaded at T ⩾ 900 K under well-controlled conditions (mode I loading, constant loading rate).
Abstract: The nucleation of dislocation loops at crack tips and the development of the plastic zone were studied in single-crystal silicon samples precracked at room temperature and loaded at T ⩾ 900 K under well-controlled conditions (mode I loading, constant loading rate). Several crystallographic orientations with different cleavage planes and crack front orientations were investigated. In situ observations by synchrotron X-ray topography were supplemented by chemical etching after fracture. Special attention was paid to the early stages of plastic zone formation. Dislocation nucleation appeared to be very heterogeneous along the crack front and may be favoured at free surfaces and cleavage edges. Activated slip systems and dislocation arrangements are discussed. It is shown that considerations based on the crack tip stress field to not suffice to account for the observed slip systems. The ledge crack mechanism of Zhou and Thomson has probably been observed but cannot be proved to be the main emission mechanism.
146 citations
15 Dec 1993
TL;DR: This work formally presents the preemption operators of the Esterel zero-delay process calculus, which is a theoretical version of the esterel synchronous programming language.
Abstract: Process preemption deals with contolling the life and death of concurrent processes. Well-defined preemption mechanisms are essential in control-dominated reactive and real-time programming, and accurate handling of preemption requires a time-dependent model. We first informally discuss what preemption is about and argue for the need of preemption primitives that are fully orthogonal with sequencing and concurrency ones. Then, we formally present the preemption operators of the Esterel zero-delay process calculus, which is a theoretical version of the Esterel synchronous programming language.
116 citations
TL;DR: In this paper, the influence of deformation temperature on the stability of the (001, 111) orientations of Al and Al-1%Mn crystals has been determined by means of channel die tests at 200-400°C.
Abstract: The influence of deformation temperature on the stability of the (001)[100] and (001)[110] orientations of Al and Al-1%Mn crystals has been determined by means of channel die tests at 200–400°C. X-ray pole figures and EBSP analyses demonstrate that the (001)[110] crystals decompose at all temperatures into deformation bands of complementary {112}〈111〉 orientations. The behaviour of the cube orientation is temperature and strain rate dependent: at T < 0.6Tm (∼ 300°C) decomposition into bands of octahedral slip occurs whereas at higher temperatures the cube orientation deforms by double slip on {110}〈110〉 systems and is stable up to high strains (ϵ ∼ 1.5). A simple analytical model and numerical simulations confirm that {110}〈110〉 slip affects the near-cube orientations and tends to stabilize the cube orientation; the latter can be considered as a hot rolling texture component.
TL;DR: In this paper, the effects of the environment and material variables on the crack growth process in alloy 718 are reviewed and analyzed on the basis of deformation characteristics in the crack tip region.
Abstract: Observations concerning the effects of the environment and material variables on the crack growth process in alloy 718 are reviewed and analyzed on the basis of deformation characteristics in the crack tip region. The review of the role of material variables has focused on the effects of chemical composition and microstructure parameters including precipitate size and morphology as well as grain size and morphology. These analyses have suggested that the governing mechanism at the crack tip is the degree of homogeneity of plastic deformation and associated slip density. For conditions promoting homogeneous plastic deformation, with a high degree of slip density, the environmental damage contribution is shown to be limited, thus permitting the dominance of cyclic damage effects which are characterized by a transgranular crack growth mode and a lower crack growth rate. Under conditions leading to inhomogeneous plastic deformation and lower slip density the crack tip damage is described in terms of grain boundary oxidation and related intergranular fracture mode. Considering that the crack growth damage mechanism in alloy 718 ranges from fully cycle dependent to fully environment dependent, conflicting experimental observations under different operating conditions are examined and a sensitizing approach is suggested to increase the alloy resistance to environmental effects.
TL;DR: Measurements of ionized calcium before and after the reaction, as well as the observation of crystals by scanning electron microspopy, allowed the hypothesis that the effect of citric acid and tartaric acid can be attributed mainly to ion pairing, in contrast to that of pyrophosphate and the other carboxylic acids.
Abstract: The nucleation and crystal growth of calcium oxalate (CaOx) were studied at pH 5.5 using turbidimetric measurements at 620 nm of suspensions produced by mixing calcium chloride and sodium oxalate (initial conditions: Ca, 3 x 10(-3) M; Ox, 0.5 x 10(-3) M). CaOx crystallization kinetics were defined first by the induction time ti and then by the slope of turbidity as a function of time during the interval corresponding to a correlation coefficient r2 > 0.99. The technique described requires only a small amount of material, is quick, convenient, and can be used to study inhibitors of CaOx crystallization by comparing ti and the rate of crystal growth in the presence and absence of inhibitors. The effects on CaOx crystal growth of several low molecular weight compounds, i.e. di- and tricarboxylic acids, were examined. The majority of these compounds were inhibitors of crystal growth, the greatest effect being seen with citric acid (50% inhibition in the presence of 1.5 x 10(-3) M citric acid), isocitric acid (50% inhibition in the presence of 0.75 x 10(-3) M isocitric acid) and pyrophosphate (30% inhibition in presence of 0.15 x 10(-3) M pyrophosphate). The inhibitors' behaviour regarding the medium was studied without any assumptions about their possible mechanisms of action. Measurements of ionized calcium before and after the reaction, as well as the observation of crystals by scanning electron microscopy, allowed us to formulate the hypothesis that the effect of citric acid and tartaric acid can be attributed mainly to ion pairing, in contrast to that of pyrophosphate and the other carboxylic acids.
TL;DR: It is pointed out that joint correspondence analysis leads to a joint display of several variables which can be calibrated in a similar fashion to recover profile elements of the subtables of the Burt matrix.
Abstract: Conditions under which correspondence analysis maps are biplots are discussed, as well as the interpretation of such biplots. It is shown that the asymmetric map which jointly displays the profiles and the vertices which define the unit vectors in the profile space is a biplot. A number of different ways of interpreting this joint plot are discussed, some of these being dependent on the choice of the x2 metric in the profile space. Biplot axes can be defined and calibrated on the zero-to-one profile scale in the usual way to recover approximations to the individual profile elements. Finally, the biplot interpretation in the context of multiple correspondence analysis is discussed. It is pointed out that joint correspondence analysis leads to a joint display of several variables which can be calibrated in a similar fashion to recover profile elements of the subtables of the Burt matrix.
15 Aug 1993-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, low cycle fatigue tests on AM1 nickel-base superalloy single crystals were conducted under axial strain control at 650, 950 and 1100 °C, and the orientation dependence of fatigue life-total strain range curves was mainly due to variations in Young's modulus with orientation.
Abstract: Low cycle fatigue tests on AM1 nickel-base superalloy single crystals were conducted under axial strain control at 650, 950 and 1100 °C. The behaviour of the [001] orientation was investigated at the three temperatures, that of the [111], [101] and [213] specimens was studied at the two lower temperatures. The orientation dependence of fatigue life-total strain range curves was mainly due to variations in Young's modulus with orientation. Most cracks grow in stege II mode whatever the temperature. Cracks nucleate at micropores and in the interior of specimens at low temperatures; surface cracks induced by oxidation are dominant at high temperatures and low strain ranges. Most of fatigue life is spent in microcrack growth.
TL;DR: In this article, the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip line density.
Abstract: — In this paper observations concerning the effects of mechanical variables on the crack growth process in alloy 718 are reviewed and analyzed on the basis of the related deformation characteristics in the crack tip region. The variables included temperature, frequency, wave shape, hold time, load ratio and load interaction. These analyses have suggested that the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip line density. On the basis of this view (which assumes crack growth damage covers the range from cyclic- to fully time-dependent processes), the interactive effects of loading parameters are discussed when considering the corresponding fracture mode. Conflicting experimental observations under different operating conditions are examined.
TL;DR: In this paper, the surface properties of powdered quasicrystalline alloys have been investigated and shown to have attractive surface mechanical properties that by-pass the brittleness inherent to quasICs and have a good corrosion resistance.
Abstract: Coatings from powdered quasicrystalline alloys may be produced. They show attractive surface mechanical properties that by-pass the brittleness inherent to quasicrystals and they have a good corrosion resistance. Examples of such results are given. An industrial application that follows is mentioned.
TL;DR: The distribution of clay minerals from the N and S Atlantic Cretaceous deep-sea sediments is related to rifting, sea floor spreading, sea-level variations and paleoceanography as mentioned in this paper.
Abstract: A B S T RA CT: The distribution of clay minerals from the N and S Atlantic Cretaceous deep-sea sediments is related to rifting, sea-floor spreading, sea-level variations and paleoceanography. Four main clay mineral suites were identified: two are inherited and indicative of ocean geodynamics, whereas the others result from transformation and authigenesis and are diagnostic of Cretaceous oceanic depositional environments. Illite and chlorite, together with interstratified illite-smectite and smectite occur above the sea-floor basalts and illustrate the contribution of volcanoclastic materials of basaltic origin to the sediments. Kaolinite, with variable amounts of illite, chlorite, smectite and interstratified minerals, indicates detrital inputs from continents near the platform margins. Kaolinite decreases upward in the series due to open marine environments and basin deepening. It may increase in volume during specific time intervals corresponding to periods of falling sea-level during which overall facies regression and erosion of the surrounding platforms occurred. Smectite is the most abundant clay mineral in the Cretaceous deep-sea sediments. Smectite-rich deposits correlate with periods of relatively low sedimentation rates. As paleoweathering profiles and basal deposits at the bottom of Cretaceous transgressive formations are mostly kaolinitic, smectite cannot have been inherited from the continents. Smectite is therefore believed to have formed in the ocean by transformation and recrystallization of detrital materials during early diagenesis. Because of the slow rate of silicate reactions, transformation of clay minerals requires a long residence time of the particles at the water/sediment interface; this explains the relationships between the observed increases in smectite with long-term sea-level rises that tend to starve the basinal settings of sedimentation. Palygorskite, along with dolomite, is relatively common in the N and S Atlantic Cretaceous sediments. It is not detrital because correlative shelf deposits are devoid of palygorskite. Palygorskite is diagnostic of Mg-rich environments and is indicative of the warm and hypersaline bottom waters of the Cretaceous Atlantic ocean.
TL;DR: In this paper, a novel in-line rheometer, called Rheopac, has been designed and built in order to study the rheological behavior of starchy products or, more generally, of products sensitive to a thermomechanical treatment.
Abstract: A novel in-line rheometer, called “Rheopac”, has been designed and built in order to study the rheological behaviour of starchy products or, more generally, of products sensitive to a thermomechanical treatment. It is based on the principle of a twin channel, using a balance of feed rate between each of them, in order to make local shear rate vary in the measuring section without changing the flow conditions into the extruder. A wide range of shear rate could be reached and measurements were performed more swiftly than with a classical slit die. The viscous behaviour of maize starch was studied by taking into account the influence of the thermomechanical history, which modified the starch degradation and thus led to important variations in the viscosity. Experimental results were satisfactorily compared to previously published models.
Journal Article•
TL;DR: In this article, geochemical analysis of hydrothermal apatite and scheelite pairs from various types of W ore deposits (skarns, disseminated scheelites, and quartz veins) provides an insight into REE partitioning between the two minerals.
Abstract: The geochemical analysis of hydrothermal apatite and scheelite pairs from various types of W ore deposits (skarns, disseminated scheelite, and quartz veins) provides an insight into REE partitioning between the two minerals. Among the 18 analyzed pairs, only five appear to have grown in equilibrium conditions. Ten other pairs show more or less important departures from equilibrium. The remaining apatite and scheelite pairs have quite different REE patterns, indicating crystallization from different fluids. Both minerals concentrate REE. The relative behavior of HREE and LREE is quite similar in the two minerals. Scheelite is only slightly more enriched in HREE relative to LREE than apatite, with K(ap-sch)La-Yb = 0.86 +/- 0.22. Beside these regularities, some dispersion in the lanthanide content ratios of apatite and scheelite, ranging from 0.6 to 5, may be related to fluid composition. The behavior of Eu can be related to redox conditions, which appear to be more oxidizing in vein associations than in skarn environments. Determination of REE in coexisting scheelite and apatite seems an efficient tool for identification of successive ore-bearing fluids.
TL;DR: In this article, the complex spherulitic structure of bulk polypropylene samples from direct scanning electron microscopy (SEM) observations of etched surfaces was investigated, showing that the slow solidification process develops a variable proportion of the monoclinic (α) and hexagonal (β) phases, ranging from 0% of β-crystals at the surface to 60 vol% of this phase at the core.
TL;DR: In this article, a simplified model of a crane is presented, which exhibits such a description of control derivatives as shown in Fig. 1 : A simplified model for a crane with control derivatives.
Abstract: Recent theoretical advances in nonlinear systems theory insist on the relevance of dynamics where control derivatives appear. We discuss here a simplified model of a crane which exhibits such a description.
TL;DR: In this paper, the elastic constants of an orthotropic material were determined by studying the free vibrations of a rectangular plate in completely free boundary conditions, based on series expansions of the deformed plate shape and requiring the boundary conditions to be satisfied.
01 Jan 1993
TL;DR: This work proposes two methods to validate the inequalities of gaussian random functions: the first is based on the acceptance-rejection technique but can be used only to validate very few inequalities; in the second, the stationary distribution of a Markov chain is sampled.
Abstract: Functions with mixed discrete/continuous distribution, random sets or coregionalizations between a function and a random set can be modelled using gaussian random functions. In these cases, the conditions at experimental points are expressed in terms of inequalities: 1 ≤ i ≤ n, a i ≤ X i ≤ b i . The simulation with composite constraints (equalities and inequalities) is performed in two steps: firstly we ensure that the inequality constraints are validated, secondly we perform a classic conditional simulation. To validate the inequalities, we propose two methods: the first one is based on the acceptance-rejection technique but can be used only to validate very few inequalities; in the second, we sample the stationary distribution of a Markov chain. This latter case is illustrated with a few examples.
TL;DR: In this paper, the wear behavior of sintered high-speed steel-type particulate composites is investigated, which depends significantly on microstructural parameters such as those of the metallic matrix and primary carbides, but also on some additional parameters related to powder metallurgy processing.
TL;DR: The thermal diffusivity of several quasicrystalline and related crystalline alloys was measured both at room temperature and as a function of temperature as discussed by the authors, and it is found remarkably small as compared to conventional metallic alloys.
Abstract: The thermal diffusivity of several quasicrystalline and related crystalline alloys was measured both at room temperature and as a function of temperature. It is found remarkably small as compared to conventional metallic alloys. It changes slightly when reversible phase transition takes place and is definitely smaller in the quasicrystalline state than in the corresponding “approximant” state.
TL;DR: In this article, a series of thin films of solid solutions of TiO2+xCr2O3 (0 < x < 0.013) and TiO 2+yNb2O5 ( 0 < y <0.05) were deposited on fused silica by means of reactive RF co-sputtering.
TL;DR: In this article, high energy milling is used for the synthesis of nanophase materials, which can be realized by direct synthesis of compounds from the elemental powders or by several exchange, transfer and mixing reactions.
01 Jan 1993
TL;DR: The connectivity of two 2-D random sets, namely the truncated gaussian model and the boolean model, is evaluated by simulation and it appears that several parameters of the random sets (porosity, integral range) affect connectivity.
Abstract: The connectivity of two 2-D random sets, namely the truncated gaussian model and the boolean model, is evaluated by simulation. It appears that several parameters of the random sets (porosity, integral range) affect connectivity. The critical values of some of these parameters are brought out.
TL;DR: Co-word analysis applied to patents through WPIL normalized title words appears to give a useful picture of a given field: both qualitative and quantitative information about the strategic aspects of the themes are obtained.
Abstract: Co-word analysis applied to patents through WPIL normalized title words appears to give a useful picture of a given field: we obtain both qualitative (themes) and quantitative information (weight of themes). It also gives information about the strategic aspects of the themes. Furthermore, in some cases, it is an indication of the future of certain themes that may help forecasting and management studies. Finally, it provides information about what could be a real technology growth process, in relation to the so-called translation model used in co-word analysis.