The impact of a sewage treatment plant's effluent on sediment quality in a small bay in Lake Geneva (Switzerland–France). Part 2: Temporal evolution of heavy metals

The Bay of Vidy is the most contaminated area of Lake Geneva, Switzerland, as a result of the release of treated and untreated waste water from the municipal sewage treatment plant of the city of Lausanne and its surroundings. The reconstruction of the historical deposition of heavy metals in the sediment of the bay has been performed by the analysis of several dated (radiocaesium) sediment cores. The presence of sewage‐derived contaminants in the Bay of Vidy since the beginning of the sewage treatment plant's operations in 1964 is clearly observed, when a sharp increase in heavy metal contents is recorded, with maximum concentrations of cadmium, copper, zinc and lead occurring between the late 1960s and early 1970s. Despite considerable improvement in recent times, the present concentrations of the investigated heavy metals in sediments of the Bay of Vidy are still higher than concentrations measured at the centre of the lake, the latter close to Lake Geneva's natural background values. It is concluded that the quantity of heavy metals deposited in the bay is considerable and, because of sediment instability, will constitute a potential hazard for biota.     

Microscopic and spectroscopic characterization of paintbrush-like single-walled carbon nanotubes

Understanding and controlling the chemical reactivity of carbon nanotubes (CNTs) is a fundamental requisite to prepare novel nanoscopic structures with practical uses in materials applications. Here, we present a comprehensive microscopic and spectroscopic characterization of carbon nanotubes which have been chemically modified. Specifically, scanning tunneling microscopy (STM) investigations of short-oxidized single-walled carbon nanotubes (SWNTs) functionalized with aliphatic chains via amide reaction reveal the presence of bright lumps both on the sidewalls and at the tips. The functionalization pattern is consistent with the oxidation reaction which mainly occurs at the nanotube tips. Thermogravimetric analysis (TGA), steady-state electronic absorption (UV-vis-NIR), and Raman spectroscopic studies confirm the STM observations.     

Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair

The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young’s modulus and thus a tool for Design Practice for repair applications.     

5-Axis tool path smoothing based on drive constraints

In high speed machining, the real feedrate is often lower than the programmed one. This reduction of the feedrate is mainly due to the physical limits of the drives, and affects machining time as well as the quality of the machined surface. Indeed, if the tool path presents sharp geometrical variations the feedrate has to be decreased to respect the drive constraints in terms of velocity, acceleration and jerk. Thus, the aim of this paper is to smooth 5-axis tool paths in order to maximize the real feedrate and to reduce the machining time.Velocity, acceleration and jerk limits of each drive allow to compute an evaluation of the maximum reachable feedrate which is then used to localize the areas where the tool path has to be smoothed. So starting from a given tool path, the proposed algorithm iteratively smoothes the joint motions in order to raise the real feedrate. This algorithm has been tested in 5-axis end milling of an airfoil and in flank milling of an impeller for which a N-buffer algorithm is used to control the geometrical deviations. An important reduction of the measured machining time is demonstrated in both examples.     

Retail competition in electricity markets

The introduction of competition into retail electricity supply gave rise to great expectations. However, to date, its performance has proven less than stellar, owing primarily to the theoretical concepts underpinning this reform, which draw heavily on the Austrian school. Neither consumers’ decision processes nor this sector's technical paradigm were adequately accounted for, leading to an uncorrect estimation of the expected impact of opening to competition. Short- and medium-term prospects for the evolution of retail markets must be reconsidered from the perspective of greater stability: not a generalization of competition, but rather a persistent segmentation between active and inactive clients; not a large and rapid diffusion of radical innovations in commercialisation, with the potential for undermining the incumbents’ positions.     

开关电源环路中的TL431

在此前一系列的3篇文章中，指出了如何采用TL431来实现1类和2类补偿器。如果前述补偿器类型适合大多数电流模式控制配置工作，其它控制模式则可能需要3类补偿器。举例来说，如果需要对连续导电模式（CCM）电压模式转换器进行补偿，就需要额外的极点和零点。在这3类配置中，TL431并不太有利于实践这样的设计：眼前的快通道（fast lane）显然会使设计工作复杂化。本文提出了简单的构想，以与所观测到交流输入完全解耦的外部直流偏置来消除快通道。这样一来，设计工作被简化，类似于采用运放来构建传统的3类补偿器。     

Isolation and analysis of macromolecular fractions responsible for the surface properties in native Champagne wines

Macromolecules present in Champagne wines from the three grape varieties Pinot Noir, Meunier and Chardonnay, were isolated by ultra-concentration on 10 K molecular weight cut-off (MWCO) membranes, then purified by dia-filtration and freeze-dried. Measurements of the surface activity of reconstituted wines from the resulting dry ultra-concentrates by ellipsometry showed the formation of adsorption layers analogous to those observed at the surface of native wines, and responsible for their foam stability. Sequential fractionation of Pinot Noir at decreasing MWCO within the 10–30 K and 30–100 K molecular weight range showed the formation of adsorption layers with both fractions. NMR and chemical analysis indicated that all fractions were mainly composed of polysaccharides and proteins. Monosaccharide analysis gave mannose, galactose, arabinose and glucose as the prominent constituting sugars. Careful bottle rinsing was found to enable thorough macromolecule recovery.     

Mechanochemical degradation of poly(vinyl fluoride) by sodium hydroxide measured by microindentation

The degradation of the mechanical properties of deformed PVDF during its mechanochemical ageing in sodium hydroxide (soda) was followed by microindentation measurements, especially the local reduction of the elastic modulus and the hardness. This allows measurements on a local scale of the mechanical properties on the surface and in-depth as a function of the strain level and the ageing time. Microindentation tests with Berkovich indenter have been performed with a Nanoindenter XP^® (MTS). Measurements are made at penetration depth less than 2 μm for an applied load of 10 mN. During ageing in soda (Ph 14) at 90 °C up to 16 days, various deformations ε (0, 22 and 38%) are imposed on PVDF tensile specimen. For the first two imposed deformations (ε = 0 and ε = 22%), mechanical degradation is limited to some percent (less than 7%). For the greatest deformation (ε = 38%), mechanical degradation continues to decrease with ageing time (more than 21%). Microindentation tests show that a range of low deformations exists in which the mechanochemical degradation is limited and no limitation is observed for larger imposed deformation.