RésuméDans une optique disciplinaire de la gouvernance, cet article propose un cadre d’analyse des contributions du comité d’audit, en termes de qualité du processus d’audit d’une part (effets ...indirects), et de qualité de l’information financière publiée d’autre part (effets directs). Une revue approfondie de la recherche empirique nous permet alors d’évaluer les principaux leviers d’action des comités d’audit, ainsi que les conditions d’efficacité de ces organes. Dans les grandes lignes, il ressort qu’un comité d’audit indépendant contribue souvent à la qualité de l’audit externe et à la fiabilité des données comptables (avec des nuances) ; et que l’expertise financière du comité stimule la fiabilité du contrôle interne et la pertinence des états financiers. Indépendance et expertise apparaissent alors comme des attributs importants et complémentaires à l’efficacité du comité d’audit. Les limites et prolongements possibles de ce courant de recherche sont discutés.
We present a measurement of the forward-backward asymmetry in the production of $B^{\pm}$ mesons, $A_{\rm FB}(B^{\pm})$, using $B^{\pm} \rightarrow J/\psi K^{\pm}$ decays in 10.4 ${\rm fb}^{-1}$ of ...$p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV collected by the D0 experiment during Run II of the Tevatron collider. A non-zero asymmetry would indicate a preference for a particular flavor, i.e., $b$ quark or $\bar{b}$ anti-quark, to be produced in the direction of the proton beam. We extract $A_{\rm FB}(B^{\pm})$ from a maximum likelihood fit to the difference between forward- and backward-produced $B^{\pm}$ mesons. We measure an asymmetry consistent with zero: $A_{\rm FB}(B^{\pm})$ = $-$0.24 $\pm$ 0.41 (stat) $\pm$ 0.19 (syst)%.
We measure the mass of the top quark in lepton+jets final states using the full sample of pp collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at sqrts = 1.96 ...TeV, corresponding to 9.7 fb(-1) of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from tt production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure m(t) = 174.98 ± 0.76 GeV. This constitutes the most precise single measurement of the top-quark mass.
Polycrystalline zinc oxide (ZnO) thin films have been deposited at 450 degree C onto glass and silicon substrates by pulsed laser deposition technique (PLD). The used source was a KrF excimer laser ...(248 nm, 25 ns, 5 Hz, 2 J/cm2). The effects of glass and silicon substrates on structural and optical properties of ZnO films have been investigated. X-ray diffraction patterns showed that ZnO films are polycrystalline with a hexagonal wurtzite-type structure with a strong (103) orientation and have a good crystallinity on monocrystalline Si(100) substrate. The thickness and compositional depth profile were studied by Rutherford Backscattering spectrometry (RBS). The average transmittance of ZnO films deposited on glass substrate in the visible range is 70%.
An austenitic stainless steel (AISI 304) has been surface implanted with nitrogen at room temperature. Ion implantation is an effective surface modification to improve the corrosion performance of ...metal materials. Using Electrochemical Impedance Spectroscopy (EIS), the electrochemical parameters which characterised the stability of passive films were calculated from the simple data of the response curves. The experimental results indicated that the stability of passive films and the pitting resistance of AISI 304 stainless steel are improved by nitrogen ion implantation.
The corrosion of underground structures, such as pipelines, depends on soil aggressiveness towards the metals. Two different methods of protection are used: (a) cathodic protection and (b) polymer ...coatings. The assessment of the degradation of buried structures is not easy because of the complex composition of the soil and its resistivity, and the risk of bacterial corrosion. Corrosion phenomena are generally studied in artificial solutions. The objective of the present paper is to study the protective capacity of coatings on pipeline steel using a “primer” paint exposed to conditions which are simulating the soil (soil simulating solution). The electrochemical behavior of uncoated and coated plates are estimated by means of electrochemical impedance spectroscopy (EIS) in two solutions: a reference media: 3 %NaCl solution, and a “soil simulating solution”. Appropriate models for impedance are used to fit the experimental data and extract the parameters which characterize the corrosion process.
Korrosionsuntersuchung eines durch einen Primer geschützten unlegierten Stahles in 3 %NaCl und in einer Boden simulierenden Lösung mit Hilfe der elektrochemischen Impedanzspektroskopie (EIS)
.Das Korrosionsverhalten von unterirdischen Bauteilen, wie z. B. Rohrleitungen, hängt von der Aggressivität des Bodens gegenüber den Metallen ab. Es werden zwei verschiedene Schutzverfahen eingesetzt: (a) kathodischer Schutz und (b) Kunststoffbeschichtungen. Aufgrund der komplexen Zusammensetzung des Bodens und seiner elektrischen Leitfähigkeit sowie des Risikos mikrobiologischer Korrosion ist die Beurteilung der Schädigung unterirdischer Teile nicht einfach. Deshalb werden Korrosionsphänomene meistens in künstlichen Lösungen untersucht. Das Ziel der vorliegenden Arbeit ist es, die Schutzwirkung von Beschichtungen auf Röhrenstahl bei Verwendung eines „Primers”︁ durch Auslagerung unter Bedingungen, die Erdboden simulieren, zu untersuchen. Das elektrochemische Verhalten von beschichteten und unbeschichteten Blechen wurde mit Hilfe der elektrochemischen Impedanzspektroskopie in zwei Lösungen beurteilt: ein Referenzmedium: 3 %NaCl Lösung, und eine „Boden simulierende Lösung”︁. Um die experimentellen Werte anzupassen und die den Korrosionsprozeß charakterisierenden Parameter zu ermitteln, wurden geeignete Modelle für die Impedanz verwendet.
PDF
