1,720,989 research outputs found
Friction for a sliding adhesive viscoelastic cylinder: Effect of Maugis parameter
Full text linkWe solve numerically the problem of a sliding viscoelastic cylinder in the presence of adhesion, modelled using the Lennard Jones force-separation law. For the material, a linear standard viscoelastic model is considered. We show the entire problem, and the friction coefficient in particular, depends on four dimensionless quantities: the Maugis–Tabor parameter λ, the dimensionless load W, the dimensionless speed V, and the ratio between the relaxed and the instantaneous modulus of the material, k=E0/E∞. For small λ, which corresponds to small rather rigid cylinders, friction returns to the classical Hunter solution for large compressive loads. For intermediate and large λ adhesion plays a significant role, and the “JKR limit” shows an adhesive component of the friction force which reaches the limit of the surface adhesion times the ratio of instantaneous to relaxed moduli at some intermediate speeds. The results obtained are in qualitative agreement with reported experimental results and can serve to guide the comparison with experiments, where it is known that the role of adhesion in rubber friction is still largely unclear and treated very often with semi-empirical equation
Friction in Rolling a Cylinder on or Under a Viscoelastic Substrate with Adhesion
Full text linkIn classical experiments, it has been found that a rigid cylinder can roll both on and under an inclined rubber plane with a friction force that depends on a power law of velocity, independent of the sign of the normal force. Further, contact area increases significantly with velocity with a related power law. We try to model qualitatively these experiments with a numerical boundary element solution with a standard linear solid and we find for sufficiently large Maugis–Tabor parameter qualitative agreement with experiments. However, friction force increases linearly with velocity at low velocities (like in the case with no adhesive hysteresis) and then decays at large speeds. Quantitative agreement with the Persson–Brener theory of crack propagation is found for the two power law regimes, but when Maugis–Tabor parameter is small, the cut-off stress in Persson–Brener theory depends on all the other dimensionless parameters of the problem
Persistent Corneal Epithelial Defect Following Pars Plana Vitrectomy: A Narrative Review
No full textPurpose: Persistent corneal epithelial defects (PCEDs) following pars plana vitrectomy (PPV) represent a significant clinical challenge, potentially leading to corneal scarring, vision loss, and other severe complications. This review aims to summarize the prevalence, associated risk factors, and management strategies for PCEDs in the context of PPV, providing evidence-based guidance for clinicians. Methods: A comprehensive systematic review was conducted using PubMed and Embase databases, identifying English-language studies addressing PCEDs after PPV. Results: The prevalence of PCEDs post-PPV varied widely, from 0% to 78.37%, influenced by intrinsic factors such as diabetes mellitus, which impairs corneal nerve function and healing, and extrinsic factors like intraoperative tamponade with C3F8. Management strategies ranged from conservative options like bandage contact lenses to advanced treatments like topical insulin. Conclusion: PCEDs after PPV are multifactorial and demand individualized management. Advanced therapies, particularly serum-based treatments, and topical insulin, show promising outcomes. Further prospective research is warranted to refine these treatments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Full text linkWe 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
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