1,720,954 research outputs found
Fatigue Analysis and Defect Size Evaluation of Filled NBR including Temperature Influence
Get PDFThe fatigue behavior of a filled non-crystallizing elastomer was investigated on axisymmetric dumbbell specimens. By plotting relevant Wöhler curves, a power law behavior was found. In addition, temperature increases due to heat build-up were monitored. In order to distinguish between initiation and crack growth regimes, hysteresis curves, secant and dynamic moduli, dissipated and stored energies, and normalized minimum and maximum forces were analyzed. Even though indications related to material damaging were observed, a clear trend to recognize the initiation was not evident. Further details were revealed by considering a fracture mechanics. The analysis of the fracture surfaces evidenced the presence of three regions, associated to initiation, fatigue striation, and catastrophic failure. Additional fatigue tests were performed with samples in which a radial notch was introduced. This resulted in a reduction in lifetime by four orders of magnitude; nevertheless, the fracture surfaces revealed similar failure mechanisms. A fracture mechanics approach, whichconsidered the effect of temperature, was adopted to calculate the critical defect size for fatigue,which was found to be approximately 9 m. This value was then compared with the particle size distribution obtained through X-ray microcomputed tomography (-CT) of undamaged samples and it was found that the majority of the initial defects were indeed smaller than the calculated one. Finally, the evaluation of J-integral for both unnotched and notched dumbbells enabled the assessment of a geometry-independent correlation with fatigue life
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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
Dipole moment modulation in push-pull diarylethenes
No full textLAUREA MAGISTRALEI materiali fotocromici sono materiali funzionali, in grado di subire una isomerizzazione reversibile a seguito di uno stimolo luminoso esterno. I due isomeri mostrano colori differenti e differenti proprietà fisico-chimiche in generale, rendendo tali materiali molto interessanti per lo sviluppo di dispositivi, come filtri modulabili, memorie ottiche o maschere riscrivibili. Tra le proprietà che variano nelle due forme, il momento di dipolo può essere sfruttato per cambiare la bagnabilità di superfici o per lo sviluppo di Organic Field Effect Transistors (OFETs) in cui il trasporto di carica nel canale semiconduttore può essere modulato tramite irraggiamento.
In questo lavoro, sono stati progettati diarileteni fotocromici che mostrassero modulazione del momento di dipolo. Specificamente, la struttura centrale 1,2-ditienilperfluorociclopentene è stata funzionalizzata nelle posizioni 5,5’ con forti gruppi donatori e accettori.
Di conseguenza, una serie omologa di diarileteni push-pull è stata sintetizzata e caratterizzata mediante spettroscopia NMR (Nuclear Magnetic Resonance), spettrometria di massa e spettroscopia infrarossa (IR). In aggiunta il loro fotocromismo è stato studiato tramite spettroscopia UV-visibile e resistenza a fatica che è una proprietà fondamentale per le reali applicazioni di tali materiali.
Il momento di dipolo elettrico permanente nelle due forme fotocromiche è stato determinato tramite misure di impedenza elettrica. I risultati sperimentali sono stati confrontati con i valori teorici e relazioni struttura-proprietà sono state messe in risalto.Photochromic materials are functional materials, which undergo a reversible isomerization due to an external luminous stimulus. The two isomers show different colours and different physical-chemical properties in general, making these materials attractive for the production of devices, such as tunable filters, rewritable optical memories or masks. Among the properties that change in the two forms, the dipole moment can be exploited in order to modulate the wettability of substrates or for the development of Organic Field Effect Transistor (OFET) where the charge transport in the semiconducting channel can be modulated upon irradiation.
In this work, photochromic diarylethenes have been designed to show a remarkable light-induced modulation of the dipole moment. Specifically, the central 1,2-dithienylperfluorocyclopentene has been functionalized at the 5,5’ positions with strong donor and acceptor groups.
Accordingly, a series of homologous push-pull diarylethenes have been synthesized and characterized through NMR spectroscopy (Nuclear Magnetic Resonance), mass spectrometry and infrared (IR) spectroscopy. Moreover, their photochromism has been studied by means of UV-vis spectroscopy and fatigue resistance, which is a fundamental property for the actual application of these materials.
The permanent electrical dipole moment in the two photochromic forms has been determined by electrical impedance measurements. The experimental results have been compared with theoretical values and structure-to-properties relationship has been highlighted
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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