1,526 research outputs found
SCIENTIFIC INTERACTIONS, GEOGRAPHIC SPILLOVERS AND INNOVATIONAN EMPIRICAL STUDY ON THE FRENCH CASE
Local and global electrochemical impedances applied to the corrosion behaviour of an AZ91 magnesium alloy
The electrochemical behaviour of an AZ91 magnesium alloy was investigated in a low aggressive medium by means of local and global electrochemical impedance measurements. The results were compared to those obtained on a pure magnesium sample. It was possible to show the individual contribution of each phase constituting the alloy, and it was observed that the corrosion mechanism of the two phases was the same, controlled by the Mg dissolution. However, local impedance diagrams clearly indicated that the kinetics dissolution of the b-phase was slower than that of the a-phase, which was in good agreement with SEM observations
Galvanic coupling between copper and aluminium in a thin-layer cell
The Al/Cu coupling was investigated in a thin-layer cell formed by a large Cu electrode and an Al microelectrode embedded in an insulator placed above the Cu electrode. By using a scanning electrochemical microscope (SECM) the thickness of the thin layer was perfectly controlledwith a precision in the micrometer range. A copper deposit on an electrochemical quartz crystal microbalance (EQCM) was also used as SECM substrate to quantify the copper dissolution rate. It was shown that such an experimental set-up allows to mimic the galvanic corrosion of intermetallic particles embedded in the aluminium matrix of the 2XXX series aluminium alloys. The combination of the SECM and the EQCM permitted the evaluation of the corrosion rate of copper at the corrosion potential of the 2024 Al alloy, whereas cyclic voltammetry performed on the SECM tip indicated the enrichment in Cu2+ ions in the thin electrolyte layer
Influence of flow on the corrosion inhibition of carbon steel by fatty amines in association with phosphonocarboxylic acid salts
This work was carried out to study the inhibition mechanism of a carbon steel in a 200 mg lâ1 NaCl solution by a non-toxic multi-component inhibitor used for water treatment in cooling circuits. The inhibitive formulation was composed of 50 mg lâ1 fatty amines associated with 200
mg lâ1 phosphonocarboxylic acid salts. Steady-state currentâvoltage curves, obtained with a rotating disc electrode, revealed that the properties of the protective layer were dependent on the electrode rotation rate and on the immersion time. The cathodic process of oxygen reduction was not modified in the presence of the inhibitive mixture. As expected, the current densities
increased when the rotation rate was increased. In the anodic range, original behaviour was observed: the current densities decreased when the electrode rotation rate increased. The morphology and the chemical composition of the inhibitive layers allowed the electrochemical results to be explained. Two distinct surface areas were visualised on the metal surface and the ratio between the two zones was dependent on the flow conditions. This behaviour was attributed to a mechanical effect linked to centrifugal force. XPS analysis revealed that the formation of a chelate between the phosphonocarboxylic acid salt molecules and the iron oxide/hydroxide was
enhanced by the increase of the electrode rotation rate
Knowledge diffusion and innovation policies within the European regions: Challenges based on recent empirical evidence
This article builds upon empirical results concerning localised knowledge spillovers to highlight some policy implications within European regions. The analysis emphasises the role of regional innovation policies in supporting the institutions that generate knowledge and learning. However, the variety of regional features presented in the empirical literature suggests that the search for universal policy tools is unrealistic. From this perspective, we argue that original strategies must be generated to cope with the various dilemmas faced by regional innovation policies. Such specific strategies require accurate knowledge of local features. Improving data and indicators to diagnose and monitor regional innovation is therefore presented as a key issue for policy makersinnovation policy ; localised knowledge flows ; European regions ; knowledge-based economy
The determinants of innovation adoption
Using a sample of 46 000 EU firms from the Community Innovation Survey, this paper analyses the drivers of innovation adoption. In contrast to most empirical studies on innovation diffusion in which a specific technology is analyzed, this study covers several countries and industries in the European Union. Following Van de Ven and Van Praag (1981), Heckman's method is applied in a context of binary endogenous variable to explain the choices made by firms regarding innovation. Distinctions are made between the internal generation of innovation and the adoption of innovation produced by others, as well as between different types of adoption (product vs. process and cooperation-based adoption vs. isolated adoption). The study is focused on the impact of users' features and their cooperation with suppliers on the adoption choices. The results point out that cooperation is a key driver of adoption choices. Usual determinants such as firm size, absorptive capability or exports would foster generation of innovation instead of adoption.Innovation adoption; Innovation diffusion; Community Innovation Survey; Process adoption; Product adoption
CPE analysis by local electrochemical impedance spectroscopy
Constant-phase elements (CPE) are used extensively in equivalent electrical circuits for fitting of experimental impedance data. The CPE behavior is generally attributed to distributed surface reactivity, surface inhomogeneity, roughness or fractal geometry, electrode porosity, and to current and potential distributions associated with electrode geometry. In this work, different electrochemical systems showing the CPE dependence in the high-frequency range for the overall impedance were considered. Local electrochemical impedance spectroscopy was found to provide a good means for assessing the influence of local variations on the CPE behavior seen in global impedance measurements. A separation between 2D and 3D distributions could be easily observed. In the case of a 2D distribution (AZ91 Mg alloy), the origin of the CPE behavior was the distribution of high-frequency resistance associated with the geometry of the disk electrode; whereas, the capacitance was independent of position. In the case of the aluminium electrode, the CPE behavior could be attributed to a combination of 3D and 2D distributions. Geometric distributions can play a significant role in the impedance response of electrochemical systems, and these distributions can lead to CPE behavior
La société en mouvement : la Belgique sur une voie de développement durable?
Vingt ans aprĂšs le Sommet de la Terre de Rio, la sociĂ©tĂ© belge est-elle sur une voie de dĂ©veloppement durable ? Ou bien sommes-nous engagĂ©s sur la pente dâun inĂ©luctable dĂ©clin ? Deux rĂ©dacteurs, tous deux de la « gĂ©nĂ©ration Rio » dans deux communautĂ©s de ce pays, ont relevĂ© le dĂ©fi dâexplorer ensemble cette question dans la premiĂšre partie de La sociĂ©tĂ© en mouvement. Cette mĂȘme question a Ă©tĂ© posĂ©e aux personnalitĂ©s issues de diffĂ©rents groupes sociĂ©taux. Femmes, jeunes, immigrĂ©s, ong, autoritĂ©s locales, travailleurs, employeurs, agriculteurs, ... : des co-auteurs reprĂ©sentant ces groupes ou les connaissant bien y commentent cette Ă©volution, leurs expĂ©riences et leurs espĂ©rances. Dans la troisiĂšme partie, des experts se demandent si nous mesurons bien les enjeux de notre dĂ©veloppement et comment les plus jeunes, aujourdâhui, sont prĂ©parĂ©s Ă lâavenir qui les attend. Les constats de La sociĂ©tĂ© en mouvement sont parfois surprenants mais ils sont convergents au moins sur un point: les dĂ©fis sont colossaux et doivent dâurgence ĂȘtre relevĂ©s. Le titre de la derniĂšre partie est Ă©loquent : 'Appel Ă lâaction urgente pour accĂ©lĂ©rer la transition'
LA PUISSANCE PUBLIQUE PROMOTEUR DE NOUVEAUX CRITERES DE DECISION DE FINANCEMENT DES ENTREPRISES
Ce texte est Ă paraĂźtre dans l'ouvrage E. Chatel, T. Kirat et R. Salais (Eds) : Action publique, L'Harmattan.La double nĂ©cessitĂ© Ă laquelle se trouve confrontĂ©e la puissance publique - dynamisation de la croissance au moyen de l'aide aux entreprises et renforcement des rĂšgles prudentielles transnationales - invite Ă se demander dans quelle mesure les divergences rĂ©sultant de la mise en application simultanĂ©e de critĂšres de sĂ©lection opposĂ©s peuvent ĂȘtre attĂ©nuĂ©es, voire compensĂ©es, par la mise en Ćuvre de modes de dĂ©cision alternatifs. En d'autres termes, comment la puissance publique peut-elle promouvoir l'adoption d'un point de vue de financeur ni totalement soumis aux ratios de solvabilitĂ© habituellement privilĂ©giĂ©s par les Ă©tablissements financiers, ni exclusivement guidĂ© par des considĂ©rations d'ordre territorial, souvent incarnĂ©es dans le nombre d'emplois crĂ©Ă©s, qui intĂ©ressent davantage les organismes d'aide et de subvention ? Cette interrogation vaut aussi pour les relations entre l'emprunteur et le prĂȘteur, encore trop dominĂ©es par la volontĂ© d'inciter le premier Ă mieux tenir compte des exigences du second sans que la rĂ©ciproque ne soit vraie. Partant de l'hypothĂšse que la discrimination entre entreprises capables d'ĂȘtre pĂ©rennes et entreprise qui le seront moins dĂ©passe le seul cadre de l'analyse financiĂšre, ce texte vise Ă mettre en Ă©vidence le rĂŽle que peut jouer la puissance publique dans un contexte de dĂ©mographie Ă©conomique turbulent. Il apparaĂźtra que si l'objectif est la survie des entreprises et la stabilisation du parc, les outils d'Ă©valuation ex ante de la qualitĂ© doivent diffĂ©rer de ceux qui guident les dĂ©cideurs prĂ©occupĂ©s par un objectif de crĂ©ation d'entreprises et d'accroissement de l'activitĂ©. Le changement de cadre d'analyse pouvant difficilement s'opĂ©rer de maniĂšre spontanĂ©e compte tenu des routines observĂ©es dans le domaine de l'Ă©valuation de la fiabilitĂ© des entrepreneurs par les principaux organismes concernĂ©s, l'intervention de la puissance publique semble Ă mĂȘme de faciliter la diffusion de critĂšres diffĂ©rents de ceux actuellement utilisĂ©s pour dĂ©cider de l'attribution de financements
Localized approach to galvanic coupling in an aluminumâmagnesium system
The corrosion behavior of a pure aluminum/pure magnesium couple in a weakly conductive sodium sulfate solution was investigated. Potential and current distributions on the surface of the model couple at the beginning of immersion were obtained by solving the Laplace equation using a finite element method algorithm. Magnesium acted as the anode of the system while oxygen and water were reduced on aluminum. Calculations predicted a large current peak at the Al/Mg interface related to a local increase in both Mg dissolution and oxygen and water reduction on aluminum, leading to a local pH increase. Optical and scanning electron microscope observations confirmed the strong dissolution of magnesium concomitantly with depassivation of aluminum at the Al/Mg interface. Local electrochemical impedance spectroscopy showed the detrimental effects of the galvanic coupling both on aluminum and magnesium
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