Recent trends in perfluorinated sulfoximines

The search for original perfluorinated moieties is a very modern and attractive challenge. Among the emergent groups, the S-perfluoroalkylated sulfoximines are very peculiar because of their structural diversity and promising properties. A literature survey shows that interest in these molecules is strongly increasing. This short review summarizes the recent works devoted to this topic.     

Herding and idiosyncratic choices: Nonlinearity and aging-induced transitions in the noisy voter model

We consider the herding-to-non-herding transition caused by idiosyncratic choices or imperfect imitation in the context of the Kirman Model for financial markets, or equivalently the Noisy Voter Model for opinion formation. In these original models, this is a finite-size transition that disappears for a large number of agents. We show how the introduction of two different mechanisms makes this transition robust and well defined. A first mechanism is nonlinear interactions among agents taking into account the nonlinear effect of local majorities. The second one is aging, so that the longer an agent has been in a given state the more reluctant she becomes to change state.     

Maximum and Comparison Principles for Convex Functions on the Heisenberg Group

Abstract

We prove estimates, similar in form to the classical Aleksandrov estimates, for a Monge–Ampère type operator on the Heisenberg group. A notion of normal mapping does not seem to be available in this context and the method of proof uses integration by parts and oscillation estimates that lead to the construction of an analogue of Monge–Ampère measures for convex functions in the Heisenberg group.     

基于ARM和DSP的钻井控制和信息传输平台的研究

为了抑制粘滑振动和监控钻井过程,需要对钻井过程进行控制,并将钻井参数实时地传输至监控中心。本文提出了一种基于ARM和DSP的钻井控制和信息传输平台,DSP作为算法运算中心、信息转发和协议转换器,ARM作为信息显示和数据存储单元。在系统总体框架下,重点分析了系统的软件和硬件设计方案。对系统在井场进行了现场测试,验证了该系统的可靠和稳定性以及控制算法的有效性。最后,阐明了只要性能和接口满足要求,DSP可用别的嵌入式CPU替代。     

Standard Model theory calculations and experimental tests

To present knowledge, all the physics at the Large Hadron Collider (LHC) can be described in the framework of the Standard Model (SM) of particle physics. Indeed the newly discovered Higgs boson with a mass close to 125 GeV seems to confirm the predictions of the SM. Thus, besides looking for direct manifestations of the physics beyond the SM, one of the primary missions of the LHC is to perform ever more stringent tests of the SM. This requires not only improved theoretical developments to produce testable predictions and provide experiments with reliable event generators, but also sophisticated analyses techniques to overcome the formidable experimental environment of the LHC and perform precision measurements. The present article proposes an overview of the present theoretical tools and of the experimental results in the field of strong and electroweak interactions.     

Hydrogenation of CO2 into hydrocarbons over bifunctional system Cu–ZnO/Al2O3 + HZSM-5: Effect of proximity between the acidic and methanol synthesis sites

A one-step CO₂ hydrogenation reaction into hydrocarbons (HC) using a bifunctional system constituted by a methanol synthesis catalyst [Cu–ZnO–Al₂O₃ (CZA)] and a zeolite (HZSM-5) has been studied. The influence of the catalyst bed configuration on activity, selectivity, and HC yield has been evaluated. The results obtained at T_R = 623 K, P_R = 3.0 MPa and WHSV = 6000 h⁻¹ show that CO₂ hydrogenation and hydrocarbon selectivity were strongly influenced by the proximity between oxide and zeolite, whatever the disposition of the two catalytic active sites. Indeed, the highest conversion and the best yield of hydrocarbons (mainly C₂) were obtained with the M1 bifunctional catalysts in which the oxide–zeolite proximity is the lowest. This is ascribed to the hydrogen spillover phenomenon, which does not promote the carbon chain growth.     

On the optimization of higher eigenvaluesSur l'optimisation de valeurs propres supérieures

A new approach is proposed for the study of the classical Lagrange problem on the optimal form of a column with clamped ends and a fixed volume. It is proved that there exists a column with the maximal possible value of the kth eigenvalue and that such a column is unique. A method for the numerical solution is proposed. The method is based on the analysis of the critical points of a non-linear functional related to the Lagrange problem. To cite this article: Y.V. Egorov, C. R. Mecanique 332 (2004).     

Réduction de modèle en convection naturelle par une méthode d'identificationModel Reduction in natural convection using an identification method.

In this numerical study, a natural convection Reduced Model (RM) is built by using results of a Detailed Model (DM, obtained by a pseudo-spectral method), associated with an optimisation problem. RM's structure is defined from a matrix formulation obtained after spatial discretisation of the problem local equations. RM's matrices are identified through the minimisation of a functional build on the discrepancy between DM's and RM's responses, for several values of Rayleigh number. The method is applied to a laminar steady flow in a 2D differentially heated cavity (Window problem). The RM allows one to strongly reduce computing time. To cite this article: M. Girault et al., C. R. Mecanique 332 (2004).     

Écoulement turbulent dans une cavité rotor–stator fermée de grand rapport d'aspect

A direct numerical simulation is combined with laboratory study to describe the turbulent flow in an annular high speed rotor–stator cavity. Comparisons are made for a turbulent flow characterized by a Reynolds number $\mathit{Re}=\Omega R_2^2/\nu =9.5\times {10}^4$ in a shrouded cavity of large aspect ratio $G=(R_2?R_1)/h=18.32$, where $R_1$ and $R_2$ are the inner and outer radii of the rotating disk, and h is the inter-disk space. A close agreement is found between the computed results and the experimental data for the mean and turbulent fields.? To cite this article: S. Poncet, A. Randriamampianina, C. R. Mecanique 333 (2005).