Electrodeposition of aluminum–hafnium alloy from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrochemistry of Hf(IV) and the electrodeposition of Al–Hf alloys were examined in the Lewis acidic 66.7–33.3 mol% aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt containing HfCl₄. When cyclic staircase voltammetry was carried out at a platinum disk electrode in this melt, the deposition and stripping waves for Al shifted to negative and positive potentials, respectively, suggesting that aluminum stripping is more difficult due to the formation of Al–Hf alloys. Al–Hf alloy electrodeposits containing ~13 at.% Hf were obtained on Cu rotating wire and cylinder electrodes. The Hf content in the Al–Hf alloy deposits depended on the HfCl₄ concentration in the melt, the electrodeposition temperature, and the applied current density. The deposits were composed of dense crystals and were completely chloride-free. The chloride-induced pitting corrosion potential of the resulting Al–Hf alloys was approximately +0.30 V against pure aluminum when the Hf content was above 10 at.%.     

Using shortest paths in some transshipment problems with concave costs

This paper deals with the problem of solving an uncapacitated transshipment problem with either one source and several sinks or one sink and several sources. The cost function of the problem is concave in the amount shipped on each arc and thus local optima are possible. A characterization of adjacent extreme flows in terms of corresponding arborescences is given for this type of networks.This characterization together with shortest path methods is then used to attack the problems of finding local optima and of ranking extreme points.A real-world problem and computational evidence for the usefulness of the method are produced.     

On the decisiveness of a game in a tournament

In sport tournaments in which teams are matched two at a time, it is useful for a variety of reasons to be able to quantify how important a particular game is. The need for such quantitative information has been addressed in the literature by several more or less simple measures of game importance. In this paper, we point out some of the drawbacks of those measures and we propose a different approach, which rather targets how decisive a game is with respect to the final victory. We give a definition of this idea of game decisiveness in terms of the uncertainty about the eventual winner prevailing in the tournament at the time of the game. As this uncertainty is strongly related to the notion of entropy of a probability distribution, our decisiveness measure is based on entropy-related concepts. We study the suggested decisiveness measure on two real tournaments, the 1988 NBA Championship Series and the UEFA 2012 European Football Championship (Euro 2012), and we show how well it agrees with what intuition suggests. Finally, we also use our decisiveness measure to objectively analyse the recent UEFA decision to expand the European Football Championship from 16 to 24 nations in the future, in terms of the overall attractiveness of the competition.     

A continuous stirred tank reactor investigation of the gas-phase reaction of hydroxyl radicals and toluene

A continuous stirred tank reactor (CSTR) was used to study the gas-phase reaction between HO? and toluene. HO? was generated by the in situ photolysis of nitrous acid. Flow reactor operation at steady-state conditions with a residence time of 20 min allowed investigation of primary and very rapid secondary reactions. CSTR and batch reactor experiments were also performed with selected products. Both gas-phase and aerosol products were identified by chromatography and mass spectroscopy, with total product yields between 55 and 75% of reacted carbon. Toluene reaction products included cresols, nitrocresols, nitrotoluenes, 3,5-dinitrotouluene, benzaldehyde, benzyl nitrate, nitrophenols, methyl-p-benzoquinone, glyoxal, methylglyoxal, formaldehyde, methyl nitrate, PAN, and CO. The fraction of HO? methyl hydrogen abstraction was calculated to be 0.13 ± 0.04. The ratio of reaction rate constants for nitrotoluene versus cresol formation from the HO?-adduct was calculated to be about 3.3 × 10⁴. Also, the ratio of cresol formation versus O₂ addition to the HO?-adduct was estimated to be ≥0.5 for atmospheric conditions. Comparisons of these measurements with previous values and the implications with respect to photochemical kinetics modeling of the atmosphere are discussed.     

Modelling of orthogonal cutting by incremental elastoplastic analysis and meshless method

This Note introduces an application of the meshless method to the case of machining simulation in small deformations, which is still subjected to numerical limitations. The treatment of the contact problem at the tool/chip interface is presented, and highlights the interest of the coupling of the contact law with friction. Validation results are detailed through typical example. To cite this article: E. Boudaia et al., C. R. Mecanique 337 (2009).     

Ozone–isoprene reactions: Product formation and aerosol potential

Dark-phase experiments between isoprene and O₃ are discussed. UNC outdoor chamber experiments have shown that in high-concentration systems of isoprene and O₃ (5 ppm C and 1 ppm) approximately 75% of the reacted carbon can be observed in the product formation of HCHO, CO, methacrolein, methylvinylketone, methylglyoxal, acetaldehyde, and propylene. Mechanisms were developed which gave reasonable fits to dark-phase chamber experiments of MACR, MVK, isoprene, and O₃. Experimental data and modeling results were used to generate O₃ rates of attack on MVK and MACR. An isoprene–O₃ rate of 1.67 × 10^?2 ppm^?1·min^?1 was used and is consistent with other rates reported in the literature. Dark isoprene–O₃ systems appear to form homogeneously nucleated aerosol. Most of these particles appear and remain at diameters well below the optical cutoff region (0.3–0.5 μm), as opposed to the particles from similar α-pinene–O₃ systems, which also form at smaller sizes but then grow into the optical size range (0.5 μm). Lower concentrations of α-pinene and O₃ (0.2 ppm C and 0.12 ppm) still generated substantial aerosol, but by comparison, rapid CN nucleation was not observed during a similar side-by-side system of isoprene and O₃.