86,599 research outputs found
Correlation between electrochemical impedance measurements and corrosion rate of magnesium investigated by real-time hydrogen measurement and optical imaging
No full textThe corrosion behaviour of magnesium in chloride-containing aqueous environment was investigated by
potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) performed simultaneously
with real-time hydrogen evolution measurements and optical imaging of the corroding surface.
The potentiodynamic investigation revealed substantial deviations from linearity in close proximity of
the corrosion potential. In particular, differences in the slope of the current/potential curves were
observed for small polarizations above or below the corrosion potential. These observations, suggest that
the usual method based on the use of the Stern–Geary equation to convert a value of resistance into a
value of corrosion current is inadequate. Nonetheless, a very good correlation between values of
resistances estimated by EIS and corrosion currents obtained from real-time hydrogen measurement was
found. Real-time hydrogen measurement also enabled, for the
first time, direct measurement of an
‘apparent’ Stern–Geary coefficient for magnesium. In order to rationalize the complex behaviours
experimentally observed, an electrical model for the corroding magnesium surface is presented
A mathematical description accounting for the superfluous hydrogen evolution and the inductive behaviour observed during electrochemical measurements on magnesium.
Get PDFWhen electrochemical techniques are used to probe the surface of corroding magnesium with the aim of obtaining quantitative information on the corrosion process, two peculiarities are generally observed: i) with anodic polarization, the rate of hydrogen evolution increases instead of decreasing and ii) during electrochemical impedance spectroscopy measurements, an inductive contribution is often observed at the low-frequency end of the spectra. The presence of these two phenomena clearly has an impact on the methodology that should be applied to correctly estimate corrosion rates from electrochemical data. The aim of this work is to provide a general mathematical description of the corroding magnesium surface that, under minimal a priori assumptions regarding the reaction kinetics, can account simultaneously for both superfluous hydrogen evolution and inductive response. The mathematical results are consistent with the suggestion that the superfluous hydrogen evolution is mainly related to the increase of the surface of the active corrosion front during anodic polarization. Further, the obtained results show that the inductive response is expected when, at the corrosion front, oxidation of magnesium proceeds faster than hydrogen evolution
A picture of University Students and Facebook: Perspectives for Academic Learning
No full textIn this contribution we will focus on the results of a survey on the use of Facebook by students of the University of Milano-Bicocca, which is part of a more generic survey on “media diet” and ICTs usage conducted by the Observatory on New Media (NuMediaBiOs) of the University of Milano Bicocca. Afterwards we will propose
some reflections on the use of Facebook in education in light of the results of the survey and the international scientific literatur
University Students and Technologies: Usage, Consumption and Future Trends in the Educational Context
No full textThis paper presents and discusses data on the use of technology in general and of Web 2.0 platforms and services in particular by students at the University of Milano-Bicocca. The data was obtained from a survey on media consumption habits and usage of new web technologies conducted by the university's Observatory on New Media, NuMediaBiOs. Research of this kind provides a valuable basis for the development, adaptation and improvement of existing services and offerings involving new technologies in educational contexts, given that for new technologies to be successfully integrated it is critical to have access to detailed information about how they are currently deployed by users (in this case, undergraduate students on basic degree programmes). Such analyses have implications for a range of contexts, not least for the public educational institution in which they are carried out, namely the universit
Influence of surface finishing and heat treatments on the corrosion resistance of LPBF-produced Ti-6Al-4V alloy for biomedical applications
No full textAdditive manufacturing (AM) technologies are gaining increasing attraction for biomedical applications due to the granted customizability and optimal surface topography for osteointegration. Ti-6Al-4V is one of the most promising materials due to its biocompatibility. However, excessive ions release can occur, leading to a relevant immunologic response in the surrounding tissues. Despite the corrosion behavior of the conventionally-manufactured material being well known, it should be assessed for AM-processed components, as the effect of the unique superficial and microstructural features granted by the process is still quite unknown. The aim of this paper is the electrochemical evaluation of the passive current density of the laser powder bed fusion (LPBF)-processed Ti-6Al-4V alloy via potentiostatic tests, carried out at typical in-service potentials for biomedical implants. This parameter is correlated with the ion release rate of the alloy, a fundamental phenomenon to address to prevent possible inflammations caused by the implant. Different manufacturing conditions (surface finishing, heat treatment) and exposure time (0, 60 and 6000 h) were considered. The importance of performing these measurements over a long period (> 8 months) was demonstrated. In fact, despite the initial current densities being significantly affected by the surface and microstructural differences, the ion release rates converged for long-time exposures. The results also underlined the good corrosion resistance of the material. Poor corrosion performances, alongside with significant current densities development, were observed in the as-built condition. A pickling treatment demonstrated to mitigate such effect without compromising the unique surface finishing granted by the manufacturing technology
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Stress corrosion cracking of additively manufactured alloy 625
Get PDFLaser bed powder fusion (LPBF) is an additive manufacturing technology for the fabrication of semi-finished components directly from computer-aided design modelling, through melting and consolidation, layer upon layer, of a metallic powder, with a laser source. This manufacturing technique is particularly indicated for poor machinable alloys, such as Alloy 625. However, the unique microstructure generated could modify the resistance of the alloy to environment assisted cracking. The aim of this work was to analyze the stress corrosion cracking (SCC) and hydrogen embrittlement resistance behavior of Alloy 625 obtained by LPBF, both in as-built condition and after a standard heat treatment (grade 1). U-bend testing performed in boiling magnesium chloride at 155 and 170◦C confirmed the immunity of the alloy to SCC. However, slow strain rate tests in simulated ocean water on cathodically polarized specimens highlighted the possibility of the occurrence of hydrogen embrittlement in a specific range of strain rate and cathodic polarization. The very fine grain size and dislocation density of the thermally untreated specimens appeared to increase the hydrogen diffusion and embrittlement effect on pre-charged specimens that were deformed at the high strain rate. Conversely, heat treatment appeared to mitigate hydrogen embrittlement at high strain rates, however at the slow strain rate all the specimens showed a similar behavior
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
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