An axiomatic characterization of the ranking based on the h-index and some other bibliometric rankings of authors

In the last few years, many new bibliometric rankings or indices have been proposed for comparing the output of scientific researchers. We propose a formal framework in which rankings can be axiomatically characterized. We then present a characterization of some popular rankings. We argue that such analyses can help the user of a ranking to choose one that is adequate in the context where she/he is working.     

Image segmentation by a contrario simulation

Segmenting an image into homogeneous regions generally involves a decision criterion to establish whether two adjacent regions are similar. Decisions should be adaptive to get robust and accurate segmentation algorithms, avoid hazardous a priori and have a clear interpretation. We propose a decision process based on a contrario reasoning: two regions are meaningfully different if the probability of observing such a difference in pure noise is very low. Since the existing analytical methods are intractable in our case, we extend them to allow a mixed use of analytical computations and Monte-Carlo simulations. The resulting decision criterion is tested experimentally through a simple merging algorithm, which can be used as a post-filtering and validation step for existing segmentation methods.     

Effect of initial powder type on the hydrogen storage properties of high-pressure torsion consolidated Mg

While severe plastic deformation (SPD) on bulk samples has been widely applied for modifying the H-sorption properties, there has been little attention towards the use of SPD on powder materials. In this context, the aim of the present work was to compare the H-storage properties of high-pressure torsion (HPT) consolidated products obtained from two distinct Mg powder precursors: atomized micro-sized and condensed ultrafine powder particles. The results showed that the nature of the initial powder precursor had a pronounced effect on the H-sorption behavior. The HPT product obtained from the condensed ultrafine powder showed faster absorption kinetics than the consolidated product obtained from the atomized powder. However, the HPT product obtained from atomized powder could absorb more hydrogen and showed faster desorption kinetics corresponding to a lower activation energy. These results are discussed by taking into account the effectiveness of the HPT process to refine the grain sizes and differences in the dispersion of fine MgO oxide particles.     

Experimental and Molecular Dynamics Simulations of Tribochemical Reactions with ZDDP: Zinc Phosphate–Iron Oxide Reaction

Zinc phosphate glass is considered to be the main constituent of tribofilms generated under boundary lubrication with zinc dialkyldithiophosphate (ZDDP), a well-known antiwear additive. The reaction occurring during friction between zinc phosphate glasses and steel native iron oxide layer is investigated by both an experimental approach and by Molecular Dynamics simulations (MD). The importance of this “tribochemical” reaction in the general ZDDP antiwear process is discussed.     

光学仿真分析在光电传感器开发过程中的应用

1 引言 光电传感器是指利用光电效应作为传感原理的传感器件,它主要由光源、光学通路、光电探测器等部分.光源发出的光照射到待检测的目标物体上,被目标物体调制后被光电探测器所接收.     

A simple analytical model to study and control azimuthal instabilities in annular combustion chambers

This study describes a simple analytical method to compute the azimuthal modes appearing in annular combustion chambers and help analyzing experimental, acoustic and large eddy simulation (LES) data obtained in these combustion chambers. It is based on a one-dimensional zero Mach number formulation where N burners are connected to a single annular chamber. A manipulation of the corresponding acoustic equations in this configuration leads to a simple dispersion relation which can be solved by hand when the interaction indices of the flame transfer function are small and numerically when they are not. This simple tool is applied to multiple cases: (1) a single burner connected to an annular chamber (N = 1), (2) two burners connected to the chamber (N = 2), and (3) four burners (N = 4). In this case, the tool also allows to study passive control methods where two different types of burners are mixed to control the azimuthal mode. Finally, a complete helicopter chamber (N = 15) is studied. For all cases, the analytical results are compared to the predictions of a full three-dimensional Helmholtz solver and a very good agreement is found. These results show that building very simple analytical tools to study azimuthal modes in annular chambers is an interesting path to control them.     

Zinc Dialkyl Phosphate (<Emphasis Type="Bold">ZP</Emphasis>) as an Anti-Wear Additive: Comparison with <Emphasis Type="Bold">ZDDP</Emphasis>

In this study, we are interested in the anti-wear properties of zinc dialkyl phosphate additive (ZP) in comparison with ‘classical’ zinc dialkyldithiophosphate (ZDDP). Friction tests were performed on a reciprocating tribometer using both ball-on-flat and cylinder-on-flat configurations under a Hertzian contact pressure of 0.9 GPa. Experiments were carried out as a function of temperature (25 and 100 °C), sliding speed (25, 50 and 100 mm/s) and additives concentrations. Ball wear scar diameters as well as friction coefficient were measured. In order to better understand the anti-wear mechanisms of these additives, friction tests were followed by surface analyses such as AES (Auger Electron Spectroscopy) and XPS (X-Ray Photoelectron Spectroscopy). Transmission Electron Microscopy (TEM) observations of the ZDDP and ZP tribofilms were also carried out to visualise the generated layers. The anti-wear capability of ZP molecule is discussed.     

On‐line acoustic attenuation spectroscopy of emulsions stabilized by vinyl alcohol–vinyl acetate copolymers: a model system for the suspension polymerization of vinyl chloride

BACKGROUND: Poly[(vinyl alcohol)‐co‐(vinyl acetate)] (PVA) copolymers obtained by partial hydrolysis of poly(vinyl acetate) are currently used as industrial stabilizers in the suspension polymerization of vinyl chloride monomer (VCM). Their molecular characteristics, mainly the average degree of hydrolysis (DH ) and average degree of polymerization (DPw ), have a major influence on the monomer droplet size and the properties of the final poly(vinyl chloride) resin. RESULTS: The average droplet size and size distribution of chlorobutane/water emulsions, as a model system for VCM/water emulsions, were studied using acoustic attenuation spectroscopy on‐line with an agitated laboratory reactor. The emulsions were stabilized by PVA with DH values between 73 and 88 mol% and DPw values between 450 and 2500. The effects of agitation speed, stirring time and concentration of the PVA copolymers were investigated. An attempt was made to correlate the interfacial tension and the droplet size. CONCLUSION: On‐line acoustic spectroscopy appears to be a suitable technique for the real‐time control of the droplet size of monomer suspensions. The advantages and limitations of the technique are outlined. The validity and the application limits of the commonly cited correlation between the droplet size and the Weber number are established for polymeric surfactant‐stabilized emulsions. Copyright © 2009 Society of Chemical Industry     

Comparison of the wound-activated transformation of caulerpenyne by invasive and noninvasive Caulerpa species of the Mediterranean

The invasive green alga, Caulerpa taxifolia, that has spread rapidly after its introduction into the Mediterranean and the North American Pacific, reacts to wounding by transforming its major metabolite caulerpenyne (1). This wound-activated reaction involves the transformation of the bis-enol acetate moiety of 1, releasing reactive 1,4-dialdehydes. The ability to perform this transformation is found also in both the noninvasive Mediterranean C. prolifera and the invasive C. racemosa. Trapping experiments, as well as transformation of the model substrate geranyl acetate, suggest that all three investigated Caulerpa spp. rely on esterases that act upon wounding of the algae by subsequently removing the three acetate residues of caulerpenyne. The resulting reactive 1,4-dialdehyde oxytoxin 2 (9) can be identified by liquid chromatography–mass spectrometry and is unstable in the wounded tissue. Caulerpenyne transformation occurs rapidly, and severe tissue damage caused degradation of more than 50% of the stored caulerpenyne within 1 min in all three algae. Prevention of the enzymatic reaction before extraction, by shock freezing the tissue with liquid nitrogen, was used for the determination of the caulerpenyne content in intact algae. It gives about twofold higher values compared to an established methanol extraction protocol. The speed and mechanism of the wound-activated transformation, as well as the caulerpenyne content in intact tissue of invasive and noninvasive Caulerpa spp., are comparable. Thus, this enzymatic , transformation, despite being fast and efficient, is likely not the key for the success of the investigated invasive species.     

Treatment of arsenic-containing solutions using chitosan derivatives: uptake mechanism and sorption performances

Modified chitosan gel beads, which had been prepared by the molybdate adsorption and coagulation (in the presence of molybdate) methods, were tested for As(III) and As(V) removal from dilute solutions (in the range 5-20 mg As L-1). The sorbent is very efficient at removing As(V) from acid solutions (optimum pH close to pH 2-3), whereas the sorption capacities are significantly lower for As(III) uptake (230 mg As(V) g-1 Mo, 70 mg As(III) g-1 Mo, respectively). Since the sorption proceeds in acidic solutions with a partial release of molybdate and with residual concentrations (ca. 500 micrograms As L-1) above the regulations for drinking water, the process appears to be directed to the treatment of industrial effluents or as a pre-concentration process. The mechanism of As(V) sorption is related to the ability of molybdate ions to complex As(V) ions in acid solutions. The uptake mechanism was confirmed by XPS analysis and desorption studies. In the case of As(III) sorption the mechanism of uptake is not identified since no complex has been cited in the literature regarding As(III) binding to Mo (VI), which was also identified by XPS analysis as the sorption site. As(V) sorption is not influenced by the presence of co-ions, with the exception of phosphate anions at low concentration, and silicate at high relative concentration. Arsenic desorption can be performed using phosphoric acid solutions.