Showing papers by "École normale supérieure de Cachan published in 1994"
TL;DR: A new class of protocols called completely specified protocols is presented, which are important because they allow for modelling unbounded fifo channels and make it possible to decide the Termination Problem, that is whether the reachability tree is finite or not.
Abstract: In this paper, we present a new class of protocols called completely specified protocols. Each protocol is represented as a system of Communicating Finite State Machines. The class of completely specified protocols is such that each message that can be received by a Finite State Machine, can also be received in every local state of the Finite State Machine. These protocols are important because they allow for modelling unbounded fifo channels and make it possible to decide the Termination Problem, that is whether the reachability tree is finite or not. An example of our techniques is given using a practical problem concerning link protocols.
86 citations
TL;DR: In this paper, the existence of a weak solution of the boundary value problem for the time dependent Vlasov-Poisson system is shown. But this solution is not suitable for the case of time dependent systems.
Abstract: In this paper we show the existence of a weak solution of the boundary value problem for the time dependent Vlasov–Poisson system. First, we regularize the system in order to apply a fixed-point theorem. Then we pass to the limit using an energy estimate.
57 citations
TL;DR: For control systems which can be locally stabilized in small time by means of a dynamic periodic time-varying state feedback law, a sufficient condition on Lie derivatives of the output is given.
Abstract: For control systems which can be locally stabilized in small time by means of a dynamic periodic time-varyingstate feedback law, we give a sufficient condition on Lie derivatives of the output for local stabilization in small time by means of a dynamic periodic time-varyingoutput feedback law If the system is analytic our sufficient condition is also necessary
55 citations
TL;DR: In this article, the authors report on the statistical analysis of experimental measurements of the crack roughness for a fracture initiated from a straight notch in a granite sample and show that the crack surface develops a self-affine character over a correlation length ξ which depends on the distance to the notch y as a power law ξ ∝ yα characterized by a dynamic exponent 1/α estimated to be 1.2 ± 0.15.
Abstract: We report on the statistical analysis of experimental measurements of the crack roughness for a fracture initiated from a straight notch in a granite sample. The crack surface is shown to develop a self-affine character over a correlation length ξ which depends on the distance to the notch y as a power law ξ ∝ yα characterized by a dynamic exponent 1/α estimated to be 1.2 ± 0.15. The self-affine roughness exponent below the correlation length is found to be 0.80 ± 0.05. The scaling is obtained from two maps of the surface, consisting each in more than 105 data points.
55 citations
TL;DR: In this article, the equations of the type det (∇ u (x )) = f in Ω and u ( x ) = x on ∂Ω where f lies in some Sobolev spaces are studied.
Abstract: Let Ω be a bounded domain in R n with regular boundary. In this paper, we study the equations of the type det (∇ u ( x )) = f in Ω and u ( x ) = x on ∂Ω where f lies in some Sobolev spaces. We establish some existence and non-existence results. A discussion of general cases is also included.
52 citations
01 Jan 1994
TL;DR: In this article, the authors investigate the mathematical validity of the multifractal formalism for functions and give some general results showing that it always yields an upper bound for the spectrum of singularities (the function that associates to each positive α the Hausdorff dimension of the set where a function F is approximately Holder of order α).
Abstract: Our purpose is to investigate the mathematical validity of the multifractal formalism for functions. We will give some general results showing that it always yields an upper bound for the spectrum of singularities (the function that associates to each positive α the Hausdorff dimension of the set where a function F is approximately Holder of order α), and we will study some examples and counterexamples of its validity, for instance, the Riemann function φ(x) = Σn−2sinn2x.
15 citations
TL;DR: In this paper, the Child-Langmuir asymptotics of a monodimensional electron beam flowing through a background of positve ions of constant density nD were considered.
Abstract: We consider the Child-Langmuir asymptotics11,5 of a monodimensional electron beam flowing through a background of positve ions of constant density nD. We extend the results valid for electron beams in the vacuum11,5 to the case of small nD’s. Large nD’s strongly modify the phase portrait of the characteristics of the Vlasov-Poisson equation and yield a different result.
13 citations
01 Jan 1994
TL;DR: In view of the considerable evidence of systematic violations of expected utility by individual subjects, a number of alternative models generalizing expected utility have been developed and the independence axiom is weakened.
Abstract: In view of the considerable evidence of systematic violations of expected utility by individual subjects, a number of alternative models generalizing expected utility have been developed. As P.Fishburn put it once [1988], we have entered “a new era” in the domain of decision under risk, but “we shall have to wait and see” during the “time of shakedown and sifting” ahead of us, i.e. until one or possibly several of the models put forward until now can attract a clear consensus. Most of these models weaken the independence axiom. But some of them retain some linearity properties, like Chew’s weighted utility theory [1983] or Fishburn’s skew-symmetric bilinear utility theory [1988]. Machina provided a quite general frame of reference, by dispensing altogether with the independence axiom and allowing one to envision different alternative hypotheses — among which his Hypothesis II [1982] is only one possibility. Other models emphasize the idea that decumulative probability distributions straightforwardly undergo a (necessarily nonlinear) cognitive transformation, like Quiggin [1982], Yaari [1987], Allais [1988], Segal [1989], Wakker [1993].
11 citations
01 Oct 1994-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: First, a surface is interpolated between data acquired on a coordinate measuring machine, and limit surfaces are computed that bind a region of space containing the known data and the most probable interpolation of the missing data of the surface.
Abstract: To acquire maximum information on the geometrical errors of industrially made surfaces at a minimum cost, a method for estimating conditional probabilities of a random signal (Bayesian prediction) is applied to three-dimensional metrology First, a surface is interpolated between data acquired on a coordinate measuring machine (CMM) Then, for a given probability, limit surfaces are computed that bind a region of space containing the known data and the most probable interpolation of the missing data of the surface These bounds can be treated as the surface; their points can be considered as if they were actual CMM data when fitting a tolerance zone or a datum feature to the data For Bayesian prediction, the basic hypotheses on the signal are stationarity, ergodicity, and gaussian density Deviations from these hypotheses and their consequences on the prediction are taken into account and corrections are proposed
10 citations
TL;DR: In this paper, the authors present the fluid equations derived by Schunck following Grad's approach to solve Boltzmann equation for near Maxwellian distribution functions, and study the hyperbolic part of these systems usually referred to as five-, eight-, 10-, 13-and 16-moment approximation.
Abstract: We present the fluid equations derived by Schunck following Grad’s approach to solve Boltzmann equation for near Maxwellian distribution functions. We study the hyperbolic part of these systems usually referred to as five-, eight-, 10-, 13- and 16-moment approximation. We show that the hyperbolicity of the systems involving the heat flux as an independent variable always requires a limitation on the heat flux. This limitation fails in the auroral ionospheric zones for the terrestrial plasma.
8 citations
TL;DR: In this article, the authors analyzed the behavior of helicoidal ends of properly embedded minimal surfaces, namely properly embedded infinite total curvature minimal annuli of parabolic type, satisfying a growth condition on the curvature via the Gauss map, and a geometric transversality condition.
Abstract: This article analyzes the behaviour of helicoidal ends of properly embedded minimal surfaces, namely properly embedded infinite total curvature minimal annuli of parabolic type, satisfying a growth condition on the curvature via the Gauss map, and a geometric transversality condition. Then we show that embeddedness forces the end to be asymptotic either to a plane, or a helicoid or a spiraling helicoid. In all three cases, the Gauss map can be described in very simple terms. Finally this local result yields a global corollary stating the rigidity of embedded minimal helicoids.
24 Oct 1994
TL;DR: This paper proposes to incorporate directional sensitivity trough the use of an antenna array to use high resolution array processing techniques, instead of traditional beamforming, to increase sensitivity.
Abstract: To increase the number of users of mobile communications we propose to incorporate directional sensitivity trough the use of an antenna array. The objective is to estimate the signal arriving from a desired emitter in the presence of noise and interfering signals. The methods we analyse in this paper perform spatial filtering to separate signals that have overlapping frequency content but originate from different spatial location. In order to increase sensitivity we propose in this paper to use high resolution array processing techniques, instead of traditional beamforming. Comparisons of these methods are made with simulations corresponding to situations which occurs in mobile communication systems.
19 Apr 1994
TL;DR: The combined use of second order backpropagation and performant initial values of the weights are applied to the extraction of parameters from real multisensor signals and show a drastic reduction in training time, improved robustness against local minima and better generalization.
Abstract: The static networks as multilayer perceptrons (MLP) are able to implement boolean logic functions, to partition the pattern space for classification problems and to approximate nonlinear functions. The present goal is to study their capabilities when used to effect a parametric estimation without an explicit model (supervised estimation). One can also consider varying parameters. The paper focuses on the combined use of second order backpropagation and performant initial values of the weights. The authors also study the effects of noise introduction into training sets in robustness and generalization faculties. These results are then applied to the extraction of parameters from real multisensor signals. They show a drastic reduction in training time, improved robustness against local minima and better generalization. >
TL;DR: In this paper, the Cauchy problem for general nonlinear dispersive equations involving derivatives in the nonlinearity is studied and the use of some decay properties of the linear part allows to address the case of arbitrarily large initial data.
Abstract: The aim of this article is to study the Cauchy problem for general nonlinear dispersive equations involving derivatives in the nonlinearity. The use of some decay properties of the linear part allows us to address the case of arbitrarily large initial data.
01 Jan 1994
TL;DR: In this article, the authors analyzed the effect of the volume effect and the stress heterogeneity effect on the failure probability of fiber-reinforced ceramics, and showed that the ultimate strength of these composites is length independent, but depends upon the stresses heterogeneity.
Abstract: Failure of ceramics is due to initial flaws. These initial flaws are in general randomly distributed within the material. An expression of the cumulative failure probability can be related to the initial flaw size distribution in the framework of the weakest link theory and independent events assumption. This approach exhibits two different effects: the volume effect and the stress heterogeneity effect. These two effects can be analyzed for fiber-reinforced ceramics. Mostly, it is shown that the ultimate strength of these composites is length independent, but depends upon the stress heterogeneity.
TL;DR: Bethuel and Ghidaglia as discussed by the authors showed that any sequence of smooth solutions to the steady incompressible two-dimensional Euler equation in a bounded domain D, which converges weakly in L2(D) as!: goes to zero, converges to a weak solution of this equation provided curlu' remains bounded in LI(D).
Abstract: 277 Bethuel, F. and J.-M. Ghidaglia, Weak limits of solutions to the steady incompressible two-dimensional Euler equation in a bounded domain, Asymptotic Analysis 8 (1994) 277-291. In this work we show that any sequence u' of smooth solutions to the steady incompressible two-dimensional Euler equation in a bounded domain D, which converges weakly in L2(D) as !: goes to zero, converges to a weak solution of this equation provided curlu' remains bounded in LI(D).
TL;DR: A general view of the Non Destructive Testing (NDT) systems based on the use of inductive sensors where the potential users are likely to be more and more numerous is presented.
Abstract: This paper presents a general view of the Non Destructive Testing (NDT) systems based on the use of inductive sensors where the potential users are likely to be more and more numerous. We describe the different phases of their conception. Firstly, we analyse the physical interaction between the sensor and the specimen material by the use of an enlarged concept of electrical images. The instrumentation problem is next reviewed by analysing the signals which are supplied by these sensors, and by the way leading to the definition of the differing range of applications of such sensors. Finally, we enumerate the various signal processing techniques usually applied in NDT and based on the general inversion techniques.
01 Jan 1994
TL;DR: In this article, a smooth, bounded and simply connected domain in ℝ 2, where ω i for i = 1, 2, n, and ω n for n = 0, ω I for n, for ω m for m = 1.
Abstract: Let G be a smooth, bounded and simply connected domain in ℝ 2 , and let ω i for i = 1,..., n, be open, smooth and simply connected subsets of G, with \( \overline {{\omega_i}} \subset G \) and \({\bar \omega _i} \cap {\bar \omega _j} = 0\). Let \( \Omega = G\backslash \mathop{ \cup }\limits_{{i = 1}}^n \overline {{\omega_i}} \) Consider the class of maps
$$ \varepsilon = \left\{ {v \in {H^1}(\Omega; {S^1})\left| {_{{\deg (v,\partial {\omega_i}) = {d_i}\;for\;i = 1,2,...,n}}^{{\deg (v,\partial ) = d\quad and}}} \right.} \right\} $$
(1)
where \( {d_i} \in Z \) are given and \( d = \sum\limits_{{i = 1}}^n {{d_i}} \).
TL;DR: In this article, the authors present a procedure experimentale composed of deux types d'epreuves: une epreuve triangulaire de determination de V˙O2 max and, une epyreuve submaximale rectangulaure, a 0% de pente, dont l'intensite est fixee a 75% de la vitesse a laquelle a ete atteint V´O2max (V˙ max).
TL;DR: This review considers the roles of the environmental signals in the context of the development of several different neural crest-derived lineages.
Abstract: Cell lineage analysis in both the central and peripheral nervous system of vertebrates has revealed that many neural progenitor cells are multipotent. These observations have raised the general issue of when and how such multipotent progenitors generate their various differentiated progeny. The environment of these progenitors controls the cell lineage decisions in the neural crest. This review considers the roles of the environmental signals in the context of the development of several different neural crest-derived lineages.
TL;DR: In this article, the integrability of the discrete Heisenberg chain was examined by applying the Integrability Criterion for differential-difference systems developed by Ramani, Grammaticos, and Tamizhmani.
24 Aug 1994
TL;DR: In this article, the authors presented applications of sensitivity functions to electrical systems supplied by static converters and gave an application to the synthesis of a digital control network of the output voltage of a variable frequency converter.
Abstract: The paper presents applications of sensitivity functions to electrical systems supplied by static converters. We give an application to the synthesis of a digital control network of the output voltage of a variable frequency converter. We use the nonlinear model of the converter and thus the computation of optimal gains for a classical control structure is valid for large variations of the entry. Simulation results illustrates the good performances of this method. >
05 Sep 1994
TL;DR: In this article, a model for switched reluctance drive fed by asymmetrical half bridges with full wave voltage in discontinuous mode is presented, and the system is linearized around its steady state to obtain a rigorous linear discrete time model which is a first order model.
Abstract: A modelling for switched reluctance drive fed by asymmetrical half bridges with full wave voltage in discontinuous mode is presented. A description of the system in terms of differential and switching equations leads directly to the sensitivities of the state vector with respect to the initial conditions. It is shown that the steady state can be obtained with Newton's method and these sensitivities. Then the system is linearized around its steady state to obtain a rigorous linear discrete time model which is a first order model. >
01 Jan 1994
TL;DR: The notion of risk is linked to the idea of potential damage as mentioned in this paper, and there are of course many kinds of risks in the financial world: default risk, the liquidity risk and the market risk.
Abstract: The notion of risk is linked to the idea of potential damage. So there are of course many kinds of risks. In the financial world the most important are: the default risk, the liquidity risk and the market risk. The default risk is the impossibility of a debtholder to keep his engagement. The liquidity risk is the temporary inability to get money from immobilizations. The market risk is the possibility to face losses, to miss opportunities or even to make profits from very fluctuating prices or rates in financial markets. So this last kind of risk is intrinsically associated with time and it is only this type of risk that we consider in this paper. Financial markets, lato sensu, are the very places where risk, time and financial decision meet.
01 Jan 1994
TL;DR: The Vlasov or Boltzmann equations, coupled with the Poisson or Maxwell equations for the fields, provide the most accurate description of the physics of charged particle transport as discussed by the authors.
Abstract: The design of many high technology components in solid-state electronics, in vacuum diode technology or in high power hyperfrequency amplification requires an accurate description of charged-particle transport. Among all the possible models, the Vlasov or the Boltzmann equations, coupled with the Poisson or Maxwell equations for the fields, provide the most accurate description of the physics of charged — particle transport. The numerical simulation of these models is an important tool for the designers.