Showing papers by "Mines ParisTech published in 1984"
TL;DR: In this paper, the axial forces induced by polycrystalline samples of Al, Cu and α-Fe of commercial purity were tested in torsion over the temperature range 20 −400, 500 and 800°C, respectively.
328 citations
TL;DR: Cognitive scientometrics is illustrated by using as data a ten-year period of articles from a biotechnology core journal, and maps of the field are given, showing connections between areas and their change over time, and with respect to the institutions in which research is performed.
Abstract: To analyse developments of scientific fields, scientometrics provides useful tools, provided one is prepared to take the content of scientific articles into account. Such cognitive scientometrics is illustrated by using as data a ten-year period of articles from a biotechnology core journal. After coding with key-words, the relations between articles are brought out by co-word analysis. Maps of the field are given, showing connections between areas and their change over time, and with respect to the institutions in which research is performed. In addition, other approaches are explored, including an indicator of lsquotheoretical levelrsquo of bodies of articles.
273 citations
TL;DR: In this article, the theoretical link between spline interpolation and kriging has been established and a theoretical comparison of splines interpolation with kriged with fixed covariance and degree of polynomial trend is made.
136 citations
TL;DR: In this paper, Fatigue crack growth rates have been determined on standard specimens containing long cracks and on specimens containing two-dimensional short cracks (∼0.10-0.50mm).
Abstract: Fatigue crack growth rates have been determined on standard specimens containing long cracks (∼5–10mm) and on specimens containing two-dimensional short cracks (∼0.10–0.50mm). Large differences have been observed indicating that at a given stress intensity factor short cracks propagate much faster than long cracks. Mouth opening displacement measurements for both specimen geometries have shown that the crack closure effect is largely responsible for the observed effect. These results are used to rationalize the behaviour of short cracks initiated from natural sites which were either graphite nodules or microshrinkage pores. The three-dimensional aspect of these natural small cracks is analysed and discussed in detail.
117 citations
113 citations
01 Dec 1984
TL;DR: This paper first defines the particular class of timed Petri nets that can be described by "linear" recurrent equations and then develops concepts such as transfer matrix representations of such systems, stability, observability, controllability, feed-back stabilization, realization of transfer matrices etc...
Abstract: In this paper, we pursue the Analogy between classical linear System Theory and a new "linear" Theory for Discrete-Event Dynamic Systems which has been introduced for the first time in [3] and which is based on the algebra of "dioids". We first define the particular class of timed Petri nets that can be described by "linear" recurrent equations and then develop concepts such as transfer matrix representations of such systems, stability, observability, controllability, feed-back stabilization, realization of transfer matrices etc...
95 citations
TL;DR: In this article, a methodology for the identification of the spatial variability of the infiltration transfer function using common climatic and piezometric data is proposed, and a parametrisation of these transfer functions using gamma distributions as basic functions is then suggested.
92 citations
TL;DR: In this article, the authors defined the notion of nearness of variogram models and quantified the sensitivity of their corresponding kriging estimators to small perturbations in data or in the variogram model.
Abstract: Current ideas of robustness in geostatistics concentrate upon estimation of the experimental variogram. However, predictive algorithms can be very sensitive to small perturbations in data or in the variogram model as well. To quantify this notion of robustness, nearness of variogram models is defined. Closeness of two variogram models is reflected in the sensitivity of their corresponding kriging estimators. The condition number of kriging matrices is shown to play a central role. Various examples are given. The ideas are used to analyze more complex universal kriging systems.
91 citations
01 Dec 1984
TL;DR: In this paper, the stability of a modified model reference adaptive controller is investigated using the L2-norm of the I/O signals of the controller and a priori knowledge about the plant is implicit.
Abstract: We study the stability given by a modified model reference adaptive controller. Modifications are projections of the adapted parameters into a compact set, normalization of the signals entering the adaptation law by a weighted L2-norm of the I/O signals. The a priori knowledge about the plant is implicit: order of a stabilizing regulator, compact set containing its coefficients. Global boundedness of the signals is established using both the error to signal approach of [10] and the operator theoretic approach of [8]. A conicity condition is involved but its robustness with respect to the graph topology of [20] is proved.
85 citations
81 citations
01 Jan 1984
TL;DR: Stochastic methods may be applied to flow problems in porous media because they are well suited to cope with the variability of the physical properties in space as discussed by the authors, but they are not suitable for flow analysis in the real world.
Abstract: Stochastic methods may be applied to flow problems in porous media because they are well suited to cope with the variability of the physical properties in space.
01 Sep 1984-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the assumption about the distribution of the polar angles of the hyperfine field direction with respect to the EFG principal axes in transition metal-metalloid amorphous alloys is discussed.
Abstract: The approximations which are made in 57Fe hyperfine field distribution calculations from magnetic amorphous alloys are discussed. A diagram which gives an immediate indication of the validity of a given hyperfine field distribution obtained using first order perturbation theory is proposed. The assumption about the distribution of the polar angles of the hyperfine field direction with respect to the EFG principal axes in transition metal-metalloid amorphous alloys is discussed. The asymmetries of the Mossbauer spectra of the latter alloys are also considered.
TL;DR: In this article, the authors derived an analytical expression for the transformed volume fraction as a function of time and showed that the influence of thickness becomes important when thickness becomes of the order of or smaller than the average spherulite radius.
Abstract: In the DSC technique, isothermal crystallization experiments are usually performed on thin flat specimens, but their interpretation generally uses theories developed for an unbounded volume. In this paper, isothermal crystallization of spherical entities in the volume limited by two parallel infinite planes is considered. Our model, derived from Avrami's theory, gives an analytical expression for the transformed volume fraction as a function of time. It is shown that the influence of thickness becomes important when thickness becomes of the order of or smaller than the average spherulite radius. The main effects of a decreasing thickness are a slower crystallization kinetics and a decrease in the Avrami exponent. These results can be used to interpret experimental data obtained in isothermal polymer crystallization.
TL;DR: The linear-k-arboricity of G (denoted lak (G)) is the minimum number of linear k-forests which partition E(G), and this new index is studied in two cases: cubic graphs and complete graphs.
TL;DR: The article ci-apres reflete l'œuvre, couronnee par le jury, which represente une voie originale and tres interessante prenant en compte, dans une modelisation a l'echelle d'un bassin hydrologique, a la fois les phenomenes superficiels and les phenomenés souterrains avec leurs interactions as mentioned in this paper.
Abstract: La societe hydrotechnique de France a decerne en 1983 le Prix Henri Milon a Monsieur Emmanuel Ledoux, pour son memoire intitule: Modelisation integree des ecoulements de surface et des ecoulements souterrains sur un bassin hydrologique. L'article ci-apres reflete l'œuvre, couronnee par le jury, qui represente une voie originale et tres interessante prenant en compte, dans une modelisation a l'echelle d'un bassin hydrologique, a la fois les phenomenes superficiels et les phenomenes souterrains avec leurs interactions.
TL;DR: In this paper, a method based on Bochner's theorem is described for demonstrating the positivedefiniteness of variogram models and for generating classes of valid variogram functions, which are then used to generate valid variograms.
Abstract: A method based on Bochner's theorem is described for demonstrating the positive-definiteness of variogram models and for generating classes of valid variogram functions.
TL;DR: In this paper, the non-isothermal flow of a power-law fluid in a coal-hanger flat die is studied, and the equilibrium and thermal equations are solved by using an iterative finite difference method.
Abstract: The non-isothermal flow of a power-law fluid in a coal-hanger flat die is studied. Equilibrium and thermal equations are solved by using an iterative finite difference method. The pressure distribution, the flow lines, the residence time distribution, the temperature distribution, and the flow uniformity at the end of the die are obtained, with a stress on the effect of thermal regulation and of temperature dependence of the viscosity.
TL;DR: In this article, a direct adaptive control scheme for not necessarily minimum phase systems is presented, which is based on simultaneous identification of input and output prediction models and leads to a bilinear parameter estimation problem for which a least-squares criterion minimization is proposed.
Abstract: A direct adaptive control scheme for not necessarily minimum phase systems is presented. The algorithm is based on simultaneous identification of input and output prediction models. This leads to a bilinear parameter estimation problem for which a least-squares criterion minimization is proposed. This framework makes it possible to establish global convergence without any extra condition. We give an example to illustrate the practical features.
01 Jan 1984
TL;DR: Factorial kriging analysis as discussed by the authors is a new method which combines Kriging and principal component analysis into the framework of geostatistics, where variables are split into principal components corresponding to different frequency ranges.
Abstract: Factorial kriging analysis is a new method which combines kriging analysis and principal component analysis into the framework of geostatistics. The variables are split into principal components corresponding to different frequency ranges.
TL;DR: In this paper, the authors present techniques decrites peuvent etre tres utiles for les indexeurs car elles permettent de produire un lexique online suggerant des macro-termes ou des synonymes.
Abstract: Les affirmations suivantes sont demontrees et illustrees par une recherche precise: 1) dans tout domaine il existe une structure generale qui est a la base de la co-occurence des termes d'indexation; 2) cette structure qui transparait dans les termes de recherche, n'est pas sensible aux variations ou aux redondances des indexeurs; 3) les articles peuvent etre classes de facon simple d'apres leurs orientations generales; 4) la liste des «poles» de cette classification peut etre directement derivee du graphe d'inclusion. Les techniques decrites peuvent etre tres utiles pour les indexeurs car elles permettent de produire un lexique online suggerant des «macro-termes» ou des synonymes. La classification des auteurs et des articles qu'elles rendent possibles, constitue une base solide pour tracer la carte de la science et de la technologie. Une telle approche permet non seulement de dessiner la structure generale ou locale d'un domaine donne, mais aussi de determiner l'importance fluctuante des contributions de chercheurs ou d'organismes dans un domaine precis. (INTD)
TL;DR: In this paper, structural changes occurring during the fatigue failure of polyester fibers have been identified, and a comparison has been made with untested fibers and fibers which were subjected to cyclic loading conditions which did not produce fatigue.
Abstract: Structural changes occurring during the fatigue failure of polyester fibers have been identified, and a comparison has been made with untested fibers and fibers which were subjected to cyclic loading conditions which did not produce fatigue. Fatigue failure was seen to result in a distinctive fracture morphology. Infrared spectrometry and X-ray diffraction revealed a lowering of crystallinity under fatigue conditions but not under other loading conditions. Transmission electron microscopy and electron diffraction revealed the creation of amorphous zones which are supposed as coalescing to form an amorphous band seen along and ahead of the fatigue crack. The zone just ahead of the fatigue crack tip is shown to contain voids. Crack propagation involves, therefore, the joining up of these voids and development along the amorphous band.
TL;DR: In this article, a Damage Mechanics model is proposed, which takes into account the initiation and propagation stages during the fatigue process, which leads to a good modelization of any creep-fatigue sequence tests or LCF tests.
TL;DR: Dans le cadre des langages infinitaires nous construisons un nouveau produit, essentiellement un produit de shuffle avec rendez-vous sur des lettres specifiques, construisant le comportement d'un systeme a partir ofi de ceux de ses composants.
TL;DR: In this article, eight creep-fatigue interaction models are identified on a set of LCF experimental data and the general agreement between tests and predictions is good in the experimental range.
TL;DR: In this paper, push-pull fatigue tests have been carried out on binary Al-5wt.%Mg specimens in the annealed and cold-worked conditions at constant plastic strain amplitudes between 4 × 10 −5 and 2 × 10−2 to characterize the cyclic stress-strain response and the strain-fatigue life behaviour.
TL;DR: Une des principales differences, actuellement, entre MEIJE et SCCS se trouve dans les limites que le calcul precedent etablit a l'interieur de sa syntaxe sur the creation of choix de comportement inifini a chaque point du processus.
TL;DR: A mechanical analysis of the forging of a coin, using an upper bound method, is briefly presented in this article, where the geometry of the coin, simplified, consists of an axisymmetric disk with a central circular design and an outer annular legend.
TL;DR: In this paper, the activation energies for amorphous alloys were determined by means of electrical resistivity measurements, the Mossbauer effect and X-ray diffraction, and the results obtained from various methods and approaches are summarized and compared.
01 Jan 1984
TL;DR: The two fold character of matter, undulatory and corpuscular, sets problems of mathematical representation which are not yet really solved The easier to picture is certainly the wave : there are numerous partial differential equations which can be used and are well studied, at least in the linear domain this paper.
Abstract: The two fold character of matter, undulatory and corpuscular, sets problems of mathematical representation which are not yet really solved The easier to picture is certainly the wave : there are numerous partial differential equations which can be used and are well studied, at least in the linear domain
TL;DR: In this article, the structure factor of an amorphous material contains both elastic and inelastic contributions and the localisation in reciprocal space and the relative weights of the elastic and elastic contributions are studied.