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Au cours de ce travail, nous avons effectué une étude méthodologique pour la préparation de banques de triazoles, en utilisant la réaction de la chimie " clic ". Ces études ont démontré que la réaction entre un alcyne vrai activé et un azoture est possible dans les conditions sans solvant et sans catalyseur pour conduire un mélange d'isomères 1,4 et 1,5 avec un rendement moyen de 76%. Nous avons remarqué que l'addition des métaux (SiO2, MgCl2, Al2O3, FeCl3 et CuCl2) permettait d'améliorer les rendements des réactions, et on a observé que la silice est la meilleur catalyseur, alors que la catalyse au cuivre (I) donne une sélectivité complète pour l'isomère 1,4. Ce résultat est bien confirmé par l'étude de la régiosélectivité qui montre que les molécules contenant deux types d'alcynes (activé et non activé) peuvent êtres fonctionnalisés séquentiellement et sélectivement. Nous avons aussi préparé les bis-triazoles en deux étapes : la première sur l'alcyne activé sans catalyseur et la deuxième étape se fait sur l'alcyne non activé par catalyse au cuivre (I), ce qui permet de dire que les alcynes terminaux portant un groupement carbonyle en de la triple liaison sont beaucoup plus réactifs.Nous avons également pu étendre l'application de la catalyse supportée dans la réaction de Huisgen dans les domaines de la synthèse de dérivés de produits naturels et d'éthers couronne. En utilisant la synthèse classique et en flux continu, nous avons pu préparer des structures originales dérivées de l'acide quinique porteuse de cycles triazoliques. Ces composés seront testés pour leur activité biologique. Nous avons également entrepris la synthèse de dérivés nouveaux d'éthers couronnes azotes afin d'incorporer à ces structures des bras contenant un ou deux noyaux triazoles. L'obtention de ces substances permettra d'ouvrir l'étude de leur propriétés complexantes dans l'avenir
The relationship of the crystallographic, magnetic, and electronic structure have long been of highinterest in research. Strontium iron oxides have structural, charge, spin, and orbital degrees offreedom, and thus give rich information to study for the condensed matter scientists. In this thesis,we have systematically studied the strontium iron oxides based on the freedom of the iron charge:Fe3+ and Fe4+ mixed valence compound SrFeO2,75 , Fe3+ compound Sr3Fe2O6 and SrFeO2,5 with differentcoordination around Fe3+ and Fe2+ compound SrFeO2. The synthesis of the polycrystalline compoundsare through either solid state reaction or sol-gel method. Single crystals of SrFeO2,75 and SrFeO2,5have been prepared by floating zone furnace. The purity of all the compounds is checked by lab x-raydiffraction and Mössbauer spectroscopy. Electronic structures have been studied by x-ray absorptionspectroscopy for all these compounds. Special efforts have been used to investigate the magneticstructure of SrFeO2,75 and Sr3Fe2O6 .
Double-walled carbon nanotubes (DWNTs), produced by a catalytic chemical vapor deposition method, have been fluorinated using a volatile mixture of BrF3 and Br2. Optical absorption spectroscopic study on the product detected nonfluorinated nanotubes, which could correspond to the inner walls of DWNTs. The fluorinated DWNTs have been annealed in vacuum at fixed temperatures, and X-ray photoelectron spectroscopy showed almost no fluorine in the sample heated to 300 °C. Comparison between X-ray fluorescent C KR spectra of the pristine DWNT sample and the annealed fluorinated sample revealed change of the atomic structure of graphitic shells in the process of thermal defluorination.
We present a mathematical study of the order book as a multidimensional continuous- time Markov chain where the order flow is modeled by independent Poisson processes. Our aim is to bridge the gap between the microscopic description of price formation (agent- based modeling), and the Stochastic Differential Equations approach used classically to describe price evolution at macroscopic time scales. To do this, we rely on the theory of infinitesimal generators and Foster-Lyapunov stability criteria for Markov chains. We motivate our approach using an elementary example where the spread is kept constant ("perfect market making"). Then we compute the infinitesimal generator associated with the order book in a general setting, and link the price dynamics to the instantaneous state of the order book. In the last section, we prove that the order book is ergodic - in particular it has a stationary distribution - that it converges to its stationary state exponentially fast, and that the large-scale limit of the price process is a Brownian motion.
In this paper, we consider a discrete time economy where we assume that the short term interest rate follows a quadratic term structure of a regime switching asset process. The possible non-linear structure and the fact that the interest rate can have different economic or financial trends justify the interest of Regime Switching Quadratic Term Structure Model (RS-QTSM). Indeed, this regime switching process depends on the values of a Markov chain with a time dependent transition probability matrix which can well captures the different states (regimes) of the economy. We prove that under this modelling that the conditional zero coupon bond price admits also a quadratic term structure. Moreover, the stochastic coefficients which appear in this decomposition satisfy an explicit system of coupled stochastic backward recursions.
In this note, we cast a Hawkes process-based order book model into a markovian setting and; using techniques from the theory of Markov chains and stochastic stability, show that the order book is stable and leads to a diffusive price limit at large time scales.
We consider allocation problems that arise in the context of service allocation in Clouds. More specifically, we assume on the one part that each computing resource is associated to a capacity constraint, that can be chosen using Dynamic Voltage and Frequency Scaling (DVFS) method, and to a probability of failure. On the other hand, we assume that the service runs as a set of independent instances of identical Virtual Machines. Moreover, there exists a Service Level Agreement (SLA) between the Cloud provider and the client that can be expressed as follows: the client comes with a minimal number of service instances which must be alive at the end of the day, and the Cloud provider offers a list of pairs (price,compensation), this compensation being paid by the Cloud provider if it fails to keep alive the required number of services. On the Cloud provider side, each pair corresponds actually to a guaranteed success probability of fulfilling the constraint on the minimal number of instances. In this context, given a minimal number of instances and a probability of success, the question for the Cloud provider is to find the number of necessary resources, their clock frequency and an allocation of the instances (possibly using replication) onto machines. This solution should satisfy all types of constraints during a given time period while minimizing the energy consumption of used resources. We consider two energy consumption models based on DVFS techniques, where the clock frequency of physical resources can be changed. For each allocation problem and each energy model, we prove deterministic approximation ratios on the consumed energy for algorithms that provide guaranteed probability failures, as well as an efficient heuristic, whose energy ratio is not guaranteed.
We give an overview of recent work on the rule-based modeling of nano devices. In particular, our experience in the modeling of a nanoscale elevator suggested us to enhance rule-based modeling with complex functional rates that can be used to express rates that depend on the current state of the entire complexes in which the reacting molecules reside.
Rule-based languages (like, for example, Kappa, BioNetGen, and BioCham) have emerged as successful models for the representation, analysis, and simulation of bio-chemical systems. In particular Kappa, although based on reactions, differs from traditional chemistry as it allows for a graph-like representation of complexes. It follows the "don't care, don't write" approach: a rule contains the description of only those parts of the complexes that are actually involved in a reaction. Hence, given any possible combination of complexes that contain the reactants, such complexes can give rise to the reaction. In this paper we address the problem of extending the "don't care, don't write" approach to cases in which the actual structure of the complexes involved in the reaction could affect it (for instance, the mass of the complexes could influence the rate). The solutions that we propose is κ F , an extension of the Kappa-calculus in which rates are defined as functions of the actually involved complexes.
Positive polynomial matrices and linear matrix inequalities (LMI) can be used to design linear parameter varying (LPV) controllers depending polynomially on the scheduling parameters, and robust to polynomial parametric uncertainty. The salient features of the approach are (a) the ability to design a controller of order and structure fixed a priori; (b) the use of a transfer function, or polynomial modeling framework that bypasses difficulties typically encountered with canonical state-space representations of LPV controllers; (c) the existence of a user-friendly Matlab interface to model this class of LMI problems. The main limitation of the approach is the choice of a nominal, or central characteristic polynomial around which the design is carried out.
In this paper we study the Poisson and heat equations on bounded and unbounded domains with smooth boundary with random Dirichlet boundary conditions. The main novelty of this work is a convenient framework for the analysis of such equations excited by the white in time and/or space noise on the boundary. Our approach allows us to show the existence and uniqueness of weak solutions in the space of distributions. Then we prove that the solutions can be identified as smooth functions inside the domain, and finally the rate of their blow up at the boundary is estimated. A large class of noises including Wiener and fractional Wiener space time white noise, homogeneous noise and Lévy noise is considered.
We consider finite energy corotationnal wave maps with target manifold $\m S^2$. We prove that for a sequence of times, they decompose as a sum of decoupled harmonic maps in the light cone, and a smooth wave map (in the blow case) or a linear scattering term (in the global case), up to an error which tends to 0 in the energy space.
An experimental approach is presented in order to study the evolution of the spreading of a macro-drop of liquid metal. The objective of this work is to supply qualitative and quantitative information during the deposit of liquid metal in static pulsed Gas Metal Arc Welding (P-GMAW). The experimental results are analyzed in the light of dimensionless numbers in order to identify the involved physical mecanisms and appreciate the heat and mass e ects on the behavior of such a macro-drop.
Several compositions of metal cored filler wire were manufactured to define the best welding conditions for homogeneous welding, by Gas Metal Arc Welding (GMAW) process, of a modified AISI 444 ferritic stainless steel dedicated to automotive exhaust manifold applications. The patented grade is know under APERAM trade name K44X and has been developed to present improved high temperature fatigue properties. All filler wires investigated contained 19%Cr and 1.8%Mo, equivalent to the base metal K44X chemistry, but various titanium and niobium contents. Chemical analyses and microstructural observations of fusion zones revealed the need of a minimum Ti content of 0.15% to obtain a completely equiaxed grain structure. This structure conferred on the fusion zone a good ductility even in the as-welded state at room temperature. Unfortunately, titanium additions decreased the oxidation resistance at 950°C if no significant Nb complementary alloying was made. The combined high Ti and Nb additions made it possible to obtain for the welded structure, after optimized heat treatment, high temperature tensile strengths and ductility for the fusion zones and assemblies, rather close to those of the base metal. 950°C aging heat treatment was necessary to restore significantly the ductility of the as welded structure. Both fusion zone and base metal presented rather homogenized properties. Finally, with the optimized composition of the cored filler wire - 0.3 Ti minimum (i.e. 0.15% in the fusion zone) and high Nb complementary additions, the properties, including the thermal fatigue strength, of the K44X assemblies are excellent.
Seven compositions of metal cored filler wires for Gas Metal Arc Welding (GMAW), containing the same weight percent of chromium (Cr) and molybdenum (Mo) as 444 steel, but with different titanium (Ti) and niobium (Nb) contents were investigated. Experimental results pointed out that the filler wire Ti content required to be twice time more than the amount expected in the deposited metal. This was due to the low Ti transfer ratio during arc welding. Moreover, Ti increased the wetting angle and promoted penetration. It was supposed that Ti affected the weld pool surface tension what led to inward Marangoni convection. Columnar to equiaxed grain transiton (CET) was also promoted thanks to the precipitation in the weld pool of Ti rich refractory compounds which act as heterogeneous nucleation sites for equiaxed grains. A minimum 0.3% Ti was required in the filler wire to form a completely equiaxed grain structure in the fusion zone. Niobium in the filler wire did not seem to have any effect on penetration, wetting and grain structure of the fusion zone.
Several characteristic waves detected by seismographs in Antarctic stations have been recognized as originating from the physical interaction between the solid earth and the atmosphere-ocean-cryosphere system surrounding the Antarctic and may be used as a proxy for characterizing ocean wave climate. A Chaparral-type infrasound sensor was installed at Syowa Station (SYO; 39.6E, 69.0S), East Antarctica, in April 2008 during the International Polar Year (IPY2007-2008). Matching data are also available for this time period from the existing broadband seismic recorder located close by. Continuous infrasound data for 2008-2009 include background signals (microbaroms) with a broad peak in the wave period between the values of 4 and 10 s. Signals with the same period are recorded by the broadband seismograph at SYO (microseisms). This period band is identified as double-frequency microseisms/baroms (DFM). The DFM have relatively lower amplitudes during winter. We suggest that this is due to the sea-ice extent around the coast causing a decreased ocean loading effect. In contrast, the single frequency microseisms/baroms with a peak in period between 12 and 30 s are observed under storm conditions, particularly in winter. On the infrasound data, stationary signals are identified with harmonic overtones at a few Hertz to lowermost human audible band, which we suggest is due to local effects such as sea-ice cracking and vibration. Microseism measurements are a useful proxy for characterizing ocean wave climate, complementing other oceanographic and geophysical data. At SYO, continuous monitoring by both broadband seismograph and infrasound contributes to the Federation of Digital Seismographic Networks, the Comprehensive Nuclear-Test-Ban Treaty in the high southern latitudes and the Pan-Antarctic Observations System under the Scientific Committee on Antarctic Research.
Three types of pathways (degradation-recondensation, natural sulphurization and selective preservation) are commonly considered for the formation of kerogen dispersed in sedimentary rocks. A fourth pathway has been recently put forward, however, from studies on Recent marine sediments, the so-called sorptive protection mechanism. This pathway is based on the adsorption of otherwise labile organic compounds onto minerals, thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen. The main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a Cenomanian kerogen. They provide (i) evidence, on an ancient material, for a crucial role of the mineral matrix both in organic matter (OM) preservation during kerogen formation and in kerogen stability once formed, (ii) indications that the dominant protective process likely involves physical protection by minerals, resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness, rather than OM adsorption as molecular monolayers and (iii) observations of the relatively poor stability of an isolated kerogen, contrary to the inertness commonly assumed for fossil macromolecular organic matter.
An efficient numerical method to compute solitary wave solutions to the free surface Euler equations is reported. It is based on the conformal mapping technique combined with an efficient Fourier pseudo-spectral method. The resulting nonlinear equation is solved via the Petviashvili iterative scheme. The computational results are compared to some existing approaches, such as the Tanaka method and Fenton's high-order asymptotic expansion. Several important integral quantities are numerically computed for a large range of amplitudes. The integral representation of the velocity and acceleration fields in the bulk of the fluid is also provided.
An efficient numerical method to compute solitary wave solutions to the free surface Euler equations is reported. It is based on the conformal mapping technique combined with an efficient Fourier pseudo-spectral method. The resulting nonlinear equation is solved via the Petviashvili iterative scheme. The computational results are compared to some existing approaches, such as the Tanaka method and Fenton's high-order asymptotic expansion. Several important integral quantities are numerically computed for a large range of amplitudes. The integral representation of the velocity and acceleration fields in the bulk of the fluid is also provided.
An improved Lozi function with alternate coefficients has been proposed. The modifications in the model allow to remove the holes in the attractor which are not desirable, but appeared in the previous Lozi function; in this way, an everywhere dense attractor can be obtained. Moreover, the strong sensitivity to the type of binarisation (conversion of real values to 0 and 1) has been demonstrated; this conversion to binary numbers is instrumental to apply the NIST tests for randomness. The results have been validated and compared via NIST tests, for the different methods of quantization. Finally, is has been verfied that the multi-random properties of the output signal have been improved thanks to the following strategies : under-sampling of the output signal, and the system order increasing. Keywords. Nonlinear dynamical system, ring-coupled map, Lozi function, NIST tests, discrete-time map, dense chaotic attractor, pseudo random number generator 1 I
The extreme characteristics of long wave run-up are studied in this paper. First we give a brief overview of the existing theory which is mainly based on the hodograph transformation (Carrier & Greenspan, 1958). Then, using numerical simulations, we build on the work of Stefanakis et al. (2011) for an infinite sloping beach and we find that resonant run-up amplification of monochromatic waves is robust to spectral perturbations of the incoming wave and resonant regimes do exist for certain values of the frequency. In the setting of a finite beach attached to a constant depth region, resonance can only be observed when the incoming wavelength is larger than the distance from the undisturbed shoreline to the seaward boundary. Wavefront steepness is also found to play a role in wave run-up, with steeper waves reaching higher run-up values.
Les tâches d'empan de mémoire de travail sont des tâches dans lesquelles des items doivent être maintenus en mémoire à court terme pendant qu'un traitement concurrent est effectué. Le but de la présente étude était de déterminer si, comme le soutient le modèle de partage temporel des ressources (Barrouillet, Bernardin, & Camos, 2004), les traitements gênent le maintien parce que les deux composantes entrent en compétition pour des processus communs ou plus simplement parce que les stratégies de maintien des items à rappeler sont perturbées par l'intrusion de l'information à traiter simultanément. Quatre-vingt sujets adultes étaient soumis à une tâche d'empan où ils devaient maintenir des lettres en même temps qu'ils devaient juger soit de la parité soit de la position spatiale de nombre présentés successivement à l'écran. Par ailleurs, ces nombres apparaissaient à un rythme régulier et donc prévisible ou bien aléatoire. Conformément à nos attentes, et contrairement à l'hypothèse d'une perturbation des stratégies de maintien, les jugements de parité qui nécessitent des récupérations en mémoire entraînaient de plus faibles empans que la tâche spatiale qui ne requiert qu'une sélection de réponse alors que le rythme de réalisation de la tâche secondaire n'avait pas d'effet sur les empans.
The functional organization of the PFC from anterior to posterior regions reflects a hierarchy of cognitive control whereby progressively anterior sub-regions are associated with higher-order control. The present study aimed at providing behavioral evidence for two predictions issuing from this cascade model. First, even the lower-most sub-part of the cognitive control hierarchy, i.e. motor programming, should interfere with higher controlled processes such as maintenance in working memory. Second, this effect should be commensurate with the time during which control is required. In a computer-paced complex span task, adults had to maintain letters while they performed a secondary task. The demand imposed by this task was manipulated either at the selection or at the motor programming stage of response preparation. Results revealed that both manipulations have a disruptive effect on verbal memory, and that this effect is commensurate with the extra-time during which response selection and motor programming require cognitive control.
Memorizing is crucial for human beings because it constitutes the fundamental step in acquiring knowledge. Among the different memory systems, the one called "working memory" works continuously to simultaneously memorize and process information. It is particularly important in children who are continually confronted to learning situations. It has long been considered that memorizing required verbalizing and repeating. The present paper offers an alternative conception: working memory relies on attentional mechanisms constrained by time and do not depend on verbal characteristics. The empirical analyses we present here do not only conduct to important theoretical conclusions, they also give a glimpse of practical applications for preventing school failure.
Several characteristic waves detected by seismographs in Antarctic stations have been recognized as originating from the physical interaction between the solid earth and the atmosphere-ocean-cryosphere system surrounding the Antarctic and may be used as a proxy for characterizing ocean wave climate. A Chaparral-type infrasound sensor was installed at Syowa Station (SYO; 39.6E, 69.0S), East Antarctica, in April 2008 during the International Polar Year (IPY2007-2008). Matching data are also available for this time period from the existing broadband seismic recorder located close by. Continuous infrasound data for 2008-2009 include background signals (microbaroms) with a broad peak in the wave period between the values of 4 and 10 s. Signals with the same period are recorded by the broadband seismograph at SYO (microseisms). This period band is identified as double-frequency microseisms/baroms (DFM). The DFM have relatively lower amplitudes during winter. We suggest that this is due to the sea-ice extent around the coast causing a decreased ocean loading effect. In contrast, the single frequency microseisms/baroms with a peak in period between 12 and 30 s are observed under storm conditions, particularly in winter. On the infrasound data, stationary signals are identified with harmonic overtones at a few Hertz to lowermost human audible band, which we suggest is due to local effects such as sea-ice cracking and vibration. Microseism measurements are a useful proxy for characterizing ocean wave climate, complementing other oceanographic and geophysical data. At SYO, continuous monitoring by both broadband seismograph and infrasound contributes to the Federation of Digital Seismographic Networks, the Comprehensive Nuclear-Test-Ban Treaty in the high southern latitudes and the Pan-Antarctic Observations System under the Scientific Committee on Antarctic Research.
Three types of pathways (degradation-recondensation, natural sulphurization and selective preservation) are commonly considered for the formation of kerogen dispersed in sedimentary rocks. A fourth pathway has been recently put forward, however, from studies on Recent marine sediments, the so-called sorptive protection mechanism. This pathway is based on the adsorption of otherwise labile organic compounds onto minerals, thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen. The main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a Cenomanian kerogen. They provide (i) evidence, on an ancient material, for a crucial role of the mineral matrix both in organic matter (OM) preservation during kerogen formation and in kerogen stability once formed, (ii) indications that the dominant protective process likely involves physical protection by minerals, resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness, rather than OM adsorption as molecular monolayers and (iii) observations of the relatively poor stability of an isolated kerogen, contrary to the inertness commonly assumed for fossil macromolecular organic matter.
An efficient numerical method to compute solitary wave solutions to the free surface Euler equations is reported. It is based on the conformal mapping technique combined with an efficient Fourier pseudo-spectral method. The resulting nonlinear equation is solved via the Petviashvili iterative scheme. The computational results are compared to some existing approaches, such as the Tanaka method and Fenton's high-order asymptotic expansion. Several important integral quantities are numerically computed for a large range of amplitudes. The integral representation of the velocity and acceleration fields in the bulk of the fluid is also provided.
Cet article présente tout d'abord comment nous nous sommes inspirés d'un paradigme issu de l'Intelligence Artificielle, le Raisonnement à Partir de Cas, pour proposer un processus permettant l'apprentissage de méthodes de résolution de problèmes fondées sur une classification des problèmes du domaine. Ce processus d'apprentissage ayant été mis en œuvre dans un EIAH destiné à enseigner la résolution de problèmes arithmétiques à l'école primaire, nous décrivons également les bases de connaissances permettant au système de dia- gnostiquer les réponses de l'élève et de lui fournir des explications.
Présentation du calcul de la distance intertextuelle et de deux méthodes de classification (classification hiérarchique ascendante, analyse arborée). Caractérisation du vocabulaire spécifique des différentes classes. Application à un groupe d'entretiens sur le confort électrique.
Largement dominant à l'époque de la production industrielle dans la grande entreprise, le contrat de travail, à durée indéterminée et à temps plein, comme mode de régulation des relations de travail, mis à la disposition par le droit du travail étatique, est à l'heure actuelle doublement concurrencé. D'un côté, l'entreprise privilégie d'autres formes juridiques de mobilisation du travail que le travail salarié et le remplace en partie par des contrats de droit commercial, afin d'échapper aux contraintes imposées par le droit du travail étatique; de l'autre côté, l'entreprise énonce elle-même des normes du travail, notamment dans le cadre de codes de conduite, destinées à régir les relations avec l'ensemble de ses travailleurs, peu important la nature juridique du lien qui existe entre ces derniers et l'entreprise. Cette nouvelle forme de régulation des relations de travail par les codes de conduite peut utilement compléter le droit du travail traditionnel, qui semble souvent mal adapté aux transformations de l'organisation de l'entreprise. Il convient cependant de considérer que ces codes, adoptés par l'entreprise, par des partenaires sociaux, ou des organisations non gouvernementales, posent des problèmes de légitimité, mais également d'efficacité, leur valeur juridique restant souvent incertaine. Afin d'éviter un affaiblissement de la protection des travailleurs, et afin de préciser la place des codes de conduite parmi les autres sources du droit du travail, on doit donc s'assurer qu'ils ne se subtituent pas aux normes traditionnelles du droit du travail, et que leur élaboration permette une participation des travailleurs.
An experimental approach is presented in order to study the evolution of the spreading of a macro-drop of liquid metal. The objective of this work is to supply qualitative and quantitative information during the deposit of liquid metal in static pulsed Gas Metal Arc Welding (P-GMAW). The experimental results are analyzed in the light of dimensionless numbers in order to identify the involved physical mecanisms and appreciate the heat and mass e ects on the behavior of such a macro-drop.
Several compositions of metal cored filler wire were manufactured to define the best welding conditions for homogeneous welding, by Gas Metal Arc Welding (GMAW) process, of a modified AISI 444 ferritic stainless steel dedicated to automotive exhaust manifold applications. The patented grade is know under APERAM trade name K44X and has been developed to present improved high temperature fatigue properties. All filler wires investigated contained 19%Cr and 1.8%Mo, equivalent to the base metal K44X chemistry, but various titanium and niobium contents. Chemical analyses and microstructural observations of fusion zones revealed the need of a minimum Ti content of 0.15% to obtain a completely equiaxed grain structure. This structure conferred on the fusion zone a good ductility even in the as-welded state at room temperature. Unfortunately, titanium additions decreased the oxidation resistance at 950°C if no significant Nb complementary alloying was made. The combined high Ti and Nb additions made it possible to obtain for the welded structure, after optimized heat treatment, high temperature tensile strengths and ductility for the fusion zones and assemblies, rather close to those of the base metal. 950°C aging heat treatment was necessary to restore significantly the ductility of the as welded structure. Both fusion zone and base metal presented rather homogenized properties. Finally, with the optimized composition of the cored filler wire - 0.3 Ti minimum (i.e. 0.15% in the fusion zone) and high Nb complementary additions, the properties, including the thermal fatigue strength, of the K44X assemblies are excellent.
Seven compositions of metal cored filler wires for Gas Metal Arc Welding (GMAW), containing the same weight percent of chromium (Cr) and molybdenum (Mo) as 444 steel, but with different titanium (Ti) and niobium (Nb) contents were investigated. Experimental results pointed out that the filler wire Ti content required to be twice time more than the amount expected in the deposited metal. This was due to the low Ti transfer ratio during arc welding. Moreover, Ti increased the wetting angle and promoted penetration. It was supposed that Ti affected the weld pool surface tension what led to inward Marangoni convection. Columnar to equiaxed grain transiton (CET) was also promoted thanks to the precipitation in the weld pool of Ti rich refractory compounds which act as heterogeneous nucleation sites for equiaxed grains. A minimum 0.3% Ti was required in the filler wire to form a completely equiaxed grain structure in the fusion zone. Niobium in the filler wire did not seem to have any effect on penetration, wetting and grain structure of the fusion zone.
Holoprosencephaly (HPE) is a common congenital defect that results from failed or incomplete forebrain cleavage. HPE is characterized by a wide clinical spectrum, with inter- and intrafamilial variability. This heterogeneity is not well understood and it has been suggested that HPE involves a combination of multiple gene mutations. In this model, several mutated alleles or modifying factors are presumed to act in synergy to cause and determine the severity of HPE. This could explain the various clinical phenotypes. Screening for HPE-associated genes in humans suggests the involvement of NODAL or SHH signaling, or both. To test this multigenic hypothesis, we investigated the effects of chemical inhibition of these two main HPE signaling pathways in a chick embryo model. SB-505124, a selective inhibitor of transforming growth factor-B type I receptors was used to inhibit the NODAL pathway. Cyclopamine was used to inhibit the SHH pathway. We report that both inhibitors caused HPE-like defects that were dependent on the drug concentration and on the developmental stage at the time of treatment. We also investigated double inhibition of NODAL and SHH pathways from the onset of gastrulation by using subthreshold inhibitor concentrations. The inhibitors of the NODAL and SHH pathways, even at low concentration, acted synergistically to promote an HPE-like phenotype. These findings support the view that genetic heterogeneity is important in the etiology of HPE and may contribute to the phenotypic variability.
We give an overview of recent work on the rule-based modeling of nano devices. In particular, our experience in the modeling of a nanoscale elevator suggested us to enhance rule-based modeling with complex functional rates that can be used to express rates that depend on the current state of the entire complexes in which the reacting molecules reside.
Rule-based languages (like, for example, Kappa, BioNetGen, and BioCham) have emerged as successful models for the representation, analysis, and simulation of bio-chemical systems. In particular Kappa, although based on reactions, differs from traditional chemistry as it allows for a graph-like representation of complexes. It follows the "don't care, don't write" approach: a rule contains the description of only those parts of the complexes that are actually involved in a reaction. Hence, given any possible combination of complexes that contain the reactants, such complexes can give rise to the reaction. In this paper we address the problem of extending the "don't care, don't write" approach to cases in which the actual structure of the complexes involved in the reaction could affect it (for instance, the mass of the complexes could influence the rate). The solutions that we propose is κ F , an extension of the Kappa-calculus in which rates are defined as functions of the actually involved complexes.
Présentation du calcul de la distance intertextuelle et de deux méthodes de classification (classification hiérarchique ascendante, analyse arborée). Caractérisation du vocabulaire spécifique des différentes classes. Application à un groupe d'entretiens sur le confort électrique.
We consider supervised learning problems within the positive-definite kernel framework, such as kernel ridge regression, kernel logistic regression or the support vector machine. With kernels leading to infinite-dimensional feature spaces, a common practical limiting difficulty is the necessity of computing the kernel matrix, which most frequently leads to algorithms with running time at least quadratic in the number of observations n, i.e., O(n^2). Low-rank approximations of the kernel matrix are often considered as they allow the reduction of running time complexities to O(p^2 n), where p is the rank of the approximation. The practicality of such methods thus depends on the required rank p. In this paper, we show that in the context of kernel ridge regression, for approximations based on a random subset of columns of the original kernel matrix, the rank p may be chosen to be linear in the degrees of freedom associated with the problem, a quantity which is classically used in the statistical analysis of such methods, and is often seen as the implicit number of parameters of non-parametric estimators. This result enables simple algorithms that have sub-quadratic running time complexity, but provably exhibit the same predictive performance than existing algorithms, for any given problem instance, and not only for worst-case situations.
To take account of the uncertainties introduced on the soft magnetic materials properties (magnetic behavior law, iron losses) during the manufacturing process, the present work deals with the stochastic modeling of the magnetic behavior law B-H and iron losses of claw pole stator generator. Twenty eight (28) samples of slinky stator (SS) coming from the same production chain have been investigated. The used approaches are similar to those used in mechanics. The accuracy of existing anhysteretic models has been tested first using cross validation techniques. The well known iron loss separation model has been implemented to take into account the variability of the losses. Then, the Multivariate Gaussian distribution is chosen to model the variability and dependencies between identified parameters, for both behavior law and iron loss models. The developed stochastic models allow predicting a 98% confidence interval for the considered samples
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