Showing papers by "University of Paris published in 1985"
TL;DR: In this paper, a model of isotropic ductile plastic damage based on a continuum damage variable, on the effective stress concept and on thermodynamics is derived, showing a large influence of triaxiality by means of a damage equivalent stress.
Abstract: A model of isotropic ductile plastic damage based on a continuum damage variable, on the effective stress concept and on thermodynamics is derived. The damage is linear with equivalent strain and shows a large influence of triaxiality by means of a damage equivalent stress. Identification for several metals is made by means of elasticity modulus change induced by damage. A comparison with the McClintock and Rice-Tracey models and with some experiments is presented for the influence of triaxiality on the strain to rupture.
2,327 citations
TL;DR: The adaptive noise smoothing filter is a systematic derivation of Lee's algorithm with some extensions that allow different estimators for the local image variance and its easy extension to deal with various types of signal-dependent noise.
Abstract: In this paper, we consider the restoration of images with signal-dependent noise. The filter is noise smoothing and adapts to local changes in image statistics based on a nonstationary mean, nonstationary variance (NMNV) image model. For images degraded by a class of uncorrelated, signal-dependent noise without blur, the adaptive noise smoothing filter becomes a point processor and is similar to Lee's local statistics algorithm [16]. The filter is able to adapt itself to the nonstationary local image statistics in the presence of different types of signal-dependent noise. For multiplicative noise, the adaptive noise smoothing filter is a systematic derivation of Lee's algorithm with some extensions that allow different estimators for the local image variance. The advantage of the derivation is its easy extension to deal with various types of signal-dependent noise. Film-grain and Poisson signal-dependent restoration problems are also considered as examples. All the nonstationary image statistical parameters needed for the filter can be estimated from the noisy image and no a priori information about the original image is required.
1,475 citations
TL;DR: In this article, the authors proposed a method for tuning the magnitude of the interaction through a given bridging network by modifying the nature of the terminal ligands, which, in some way, play the role of adjusting screws.
Abstract: When two paramagnetic transition metal ions are present in the same molecular entity, the magnetic properties can be totally different from the sum of the magnetic properties of each ion surrounded by its nearest neighbors. These new properties depend on the nature and the magnitude of the interaction between the metal ions through the bridging ligands. If both ions have an unpaired electron (e.g. Cu2+ ions), then the molecular state of lowest energy is either a spin singlet or a spin triplet. In the former case, the interaction is said to be antiferromagnetic, in the latter case ferromagnetic. The nature and the order of magnitude of the interaction can be engineered by judiciously choosing the interacting metal ions and the bridging and terminal ligands, and, thus, by the symmetry and the delocalization of the orbitals centered on the metal ions and occupied by the unpaired electrons (magnetic orbitals). The first success in this “molecular engineering” of bimetallic compounds was in the synthesis of a Cu2+VO2+ heterobimetallic complex in which the interaction is purely ferro-magnetic. The same strategy could be utilized for designing molecular ferromagnets, one of the major challenges in the area of molecular materials. Another striking result is the possibility of tuning the magnitude of the interaction through a given bridging network by modifying the nature of the terminal ligands, which, in some way, play the role of “adjusting screws”. By careful selection of the bridging and terminal ligands, a very large antiferro-magnetic interaction can be achieved, even if the metal ions are far away from each other. Some sulfur-containing bridges are especially suitable in this respect.
587 citations
556 citations
TL;DR: On demontre l'unicite de solutions faibles et l'existence and l'uniformity de solutions globales fortement continues dans l'espace energie as mentioned in this paper.
Abstract: On demontre l'unicite de solutions faibles et l'existence et l'unicite de solutions globales fortement continues dans l'espace energie
347 citations
TL;DR: In this article, the existence of global weak solutions for non-linear Schrodinger equations is proved by a compactness method and, under stronger assumptions, the uniqueness of those solutions is established.
Abstract: We study the Cauchy problem for a class of non-linear Schrodinger equations. We prove the existence of global weak solutions by a compactness method and, under stronger assumptions, the uniqueness of those solutions, thereby generalizing previous results.
345 citations
TL;DR: In this paper, the authors consider des surfaces Σ parametrisees sur le disque unite: Ω={(x,y)∈R 2 ; x 2 +y 2 <1} and Σ=u(Ω), ou u:Ω→R 3 satisfait Δu=2u x u y sur Ω, |u x | 2 −|u y | 2 =u x •u y =0 sur Γ, u(∂Ω)=Γ.
Abstract: Soit Γ⊂R 3 une courbe de Jordan. On cherche des surfaces de courbure moyenne constante delimitees par Γ. On considere des surfaces Σ parametrisees sur le disque unite: Ω={(x,y)∈R 2 ; x 2 +y 2 <1} et Σ=u(Ω), ou u:Ω→R 3 satisfait Δu=2u x u y sur Ω, |u x | 2 −|u y | 2 =u x •u y =0 sur Ω, u(∂Ω)=Γ. On etudie le comportement de telles surfaces quand Γ→0
331 citations
01 Aug 1985
TL;DR: A new technique to handle complex Markov models is presented based on a description using stochastic automatas and is dedicated to distributed algorithms modelling.
Abstract: In this paper a new technique to handle complex Markov models is presented. This method is based on a description using stochastic automatas and is dedicated to distributed algorithms modelling. One example of a mutual exclusion algorithm in a distributed environment is extensively analysed. The mathematical analysis is based on tensor algebra for matrices.
319 citations
TL;DR: In this paper, a semi-groupe symetrique sousmarkovien and soit n>2 is defined, where n is the number of proprietors.
318 citations
TL;DR: In this article, the authors describe the extension of the method both to non-noble metals such as Co, Ni, Zn or Pb, where the strong reactivity of the separate metal atoms and native clusters must be overcome, and to bimetallic particles such as Cu3↕Pd which exhibit perfectly ordered structures.
Abstract: The high specific area of metallic microaggregates, together with their ability to transfer electrons more readily than the corresponding bulk metals1–4, makes this highly dispersed state of matter important in fields such as catalysis, photography and nucleation studies. But the successful preparation of very small microaggregates by radiation-induced reduction of metallic ions has only been reported for noble metals1–8. We describe here the extension of the method both to non-noble metals such as Co, Ni, Zn or Pb, where the strong reactivity of the separate metal atoms and native clusters must be overcome, and to bimetallic particles (such as Cu3↕Pd) which exhibit perfectly ordered structures9. Both kinds of aggregates have many potential applications, the foremost being in catalysis.
304 citations
01 Jun 1985
TL;DR: These transformations are powerful enough to construct all other transformations defined before, and preserve several classical properties of nets: boundednes, safety, covering by S-invariants, proper termination, home states, unavoidable states, liveness and abstraction.
Abstract: In order to make easier the verification of parallel systems, we present a set of transformations which preserve several classical properties of nets: boundednes, safety, covering by S-invariants, proper termination, home states, unavoidable states, liveness and abstraction. These transformations are powerful enough to construct all other transformations defined before. We conclude with examples of possible utilisations.
TL;DR: In this paper, the authors give the most realistic description of the concept of intracrystalline latent hardening through the analysis, at the microstructural scale of the dislocation densities, of various and complementary experimental data, and underline the excessive restriction introduced by the classical assumption of pure strain hardening in the determination of the most general single crystal hardening variation law for a wider range of loading processes.
TL;DR: Block sequential iterations of threshold networks are studied through the use of a monotonic operator, analogous to the spin glass energy, which allows to characterize the dynamics: transient and fixed points.
TL;DR: In this article, the authors propose an example of the contrary: every system of first order partial differential equations of a certain type can be solved by use of an economics principle, and for the case of a single equation their approach is in some sense dual to the usual optimal control method.
TL;DR: Basic features of quantum mechanics follow, such as the identification of observables with self-adjoint operators, and canonical quantization rules, which gives a new insight on the geometry of quantum theory.
Abstract: The generator aspect of observables in classical mechanics leads naturally to a generalized classical mechanics, of which quantum mechanics is shown to be a particular case. Basic features of quantum mechanics follow, such as the identification of observables with self-adjoint operators, and canonical quantization rules. This point of view also gives a new insight on the geometry of quantum theory: Planck's constant is related for instance to the curvature of the quantum-mechanical space of states, and the uniqueness of quantum mechanics can be proved. Finally, the origin of the probabilistic interpretation is discussed.
TL;DR: The ability of enzymatically isolated osteoblasts cultured in the presence of beta-glycerophosphate to form bone in vitro is demonstrated, and this process is similar to bone formation in vivo.
TL;DR: In this paper, the notion de solutions viscosite aux espaces de Banach reussit dans des espaces munis de la propriete de Radon-Nikodym.
TL;DR: In this paper, the authors classified the equations governing the flow of viscoelastic liquids according to the symbol of their differential operators, and discussed propagation of singularities and conditions for a change of type.
Abstract: The equations governing the flow of viscoelastic liquids are classified according to the symbol of their differential operators. Propagation of singularities is discussed and conditions for a change of type are investigated. The vorticity equation for steady flow can change type when a critical condition involving speed and stresses is satisfied. This leads to a partitioning of the field of flow into subcritical and supercritical regions, as in the problem of transonic flow.
TL;DR: In this article, the usual Sobolev inequality in ℝn, n≥3, asserts that if f = 0 on ∂ Ω, then ==================>>\s======\left\| {
abla f} \right\|_2^2 \geqslant {S_n}\left''€2 + C(\Omega )\left''| f \right�|_{2*}^2 + + C(n,w)
TL;DR: In this article, Puits multiples en mecanique semi-classique iv etude du complexe de witten are presented, and the authors discuss partial differential equations.
Abstract: (1985). Puits multiples en mecanique semi-classique iv etude du complexe de witten. Communications in Partial Differential Equations: Vol. 10, No. 3, pp. 245-340.
TL;DR: In this paper, the authors show that the asymptotic behavior of a wide class of estimators for a dynamic error component model is highly dependent on the assumption about the initial observations and that it offers very good approximations to the small sample behavior of the estimators under consideration.
TL;DR: In this article, the authors proposed a new dynamical mechanism which works most efficiently for a temperature and pressure-dependent rheology, which is capable of producing the rapid time scale of the swell uplift, of the order of 10 Myr.
Abstract: Gravitational, topographical and seismological studies of uplift regions around hot spots on oceanic,1,2 and continental plates3–7 have suggested that considerable lithospheric thinning has taken place beneath these areas. Previous models used to study this phenomenon have been based on thermal conduction8–11 and on the dynamic interaction between large-scale plume structures12 and the lithosphere, for a purely temperature-dependent viscosity. However, their predictions of the time scale for direct erosion12 of the lithosphere by these upwellings are too long. We propose here a new dynamical mechanism which works most efficiently for a temperature and pressure-dependent rheology. Our idea is that thinning of the lithosphere is accomplished by strong secondary convection enhanced by the presence of a low-viscosity zone which grows from a plume associated with a hot spot. This process is capable of producing the rapid time scale of the swell uplift13, of the order of 10 Myr, and the rates of thinning, of order 10 km Myr−1, required by both geophysical13,14 and geochemical15 observations.
TL;DR: In this paper, the electrocarboxylation of a large variety of organic halides is achieved in simple and mild conditions in diaphragm-less cells, and the results are shown to be stable.
TL;DR: On etudie des equations du type (1): −Δu+H(x,⊇u)+αu=0 dans Ω, ou est un ouvert borne regulier de R N, α≥0, H est une non-linearite donnee, fonction de x∈Ω, p∈R N. On considere (1) avec des conditions aux limites de type Neumann ou derivee oblique as discussed by the authors.
Abstract: On etudie des equations du type (1): −Δu+H(x,⊇u)+αu=0 dans Ω, ou Ω est un ouvert borne regulier de R N , α≥0, H est une non-linearite donnee, fonction de x∈Ω, p∈R N . On considere (1) avec des conditions aux limites de type Neumann ou derivee oblique
TL;DR: Soit {A(i,j); i,j∈N} la matrice stochastique d'une chaine de Markov reversible sur N={1,2,...}. Soit n≥2 tel que ∥f∥ r ≤C∥f ∥ D ; ∀f∈C 0 (N) ou r=2n/(n-2), ou C>0 est independant de f et ou ∥• r indique la norme dans l r (N; dλ)
TL;DR: These experiments were able to offer to 134 subjects the possibility of actually gaining or losing an important sum of money by exploiting the ‘isolation effect’ and show that under risk as well as under complete ignorance the subjects' attitudes towards prospects of gains and toward prospects of losses are totally unrelated.
Abstract: These experiments are concerned with individual behavior under risk and under uncertainty. By exploiting the ‘isolation effect’ the experiments were able to offer to 134 subjects the possibility of actually gaining or losing an important sum of money.
TL;DR: The structural setting of major alkaline provinces in Africa are reviewed and compared with examples from Siberia, Europe, southern Greenland, and North America as discussed by the authors, and it is concluded that the lithosphere has a very active role.
TL;DR: In this paper, the authors considered a system of identical interacting particles moving on the lattice Ω¯¯¯¯ d fixme, where the rate at which a particle at the site x jumps to the site y is p(y−x)b(η(x), η(y)) where p is an irreducible probability on ℤ d istg d istg and b(x, η (y)) is an increasing (resp. decreasing) function of the number of particles at site x.
Abstract: We consider a system of identical interacting particles moving on the lattice ℤ
d
. The rate at which a particle at the site x jumps to the site y is p(y−x)b(η(x), η(y)) where p is an irreducible probability on ℤ
d
and b(η(x), η(y)) is an increasing (resp. decreasing) function of the number η(x) (resp. η(y)) of particles at site x (resp. y). We study the convergence of the system to equilibrium and describe the invariant measures.
TL;DR: In this article, all possible anomalous terms in quantum gauge theory in the natural class of polynomials of differential forms were computed using the appropriate cohomological and algebraic methods, for all dimensions of spacetime and all structure groups with reductive Lie algebras.
Abstract: We compute all possible anomalous terms in quantum gauge theory in the natural class of polynomials of differential forms. By using the appropriate cohomological and algebraic methods, we do it for all dimensions of spacetime and all structure groups with reductive Lie algebras.