1,720,955 research outputs found
Laser percussion micro-drilling on PBF-LB/M-manufactured CoCrMo alloy plates: process characterisation and comparison with additively manufactured holes
Full text linkThe paper deals with the laser micro-drilling of CoCrMo superalloy sheets, 1.5 mm in thickness, manufactured via powder bed fusion by laser beam melting (PBF-LB/M) technology, by percussion drilling techniques. Laser drilling tests were carried out using a 450/4500 QCW pulsed fiber laser with a pulse power of up to 4.5 kW. The experimental tests were performed adopting a Box-Behnken design. During the tests, the pulse power, pulse duration, assistant gas pressure, focus position, and total released energy were varied. Hole geometries were characterised at the beam entrance and exit by adopting a 3D digital microscope. The entrance and exit diameters, roundness, taper angle, spatter area, and maximum dross height were analysed. ANalysis Of VAriance (ANOVA) and Response Surface Methodology (RSM) were adopted to investigate the influence of the process parameters and model the process. The geometrical characteristics of the laser-drilled holes were compared to additively manufactured ones. Multi-Objective-Optimization (MRO) was adopted to identify optimal process conditions to produce micro-holes with an imposed diameter and minimal taper angle. Then, the RSM model was experimentally validated, showing a strong correlation with predicted values up to 600 μm. Moreover, the geometry of additively manufactured holes was characterised too, and the mechanisms of defect generation were discussed. From the result, comparing the geometry of the laser-drilled holes to the ones obtained by additive manufacturing, the former technique is particularly competitive in the diameter range of 300–600 μm
A Preliminary Study on Fatigue Behavior of Aluminum Single‐Lap Joints Subjected to Laser Surface Treatments
No full textThe study deals with the effects of laser surface treatments on the fatigue behavior of adhesive-bonded aluminum joints. Laser texturing, laser cleaning, and their combination are produced by adopting a 30 W nanosecond pulsed Yb:YAG laser. Parallel grooves, perpendicular to the load direction, varying in depth, width, and areal density are adopted as textured geometrical features. To assess the performance of laser treatments a central composite design (CCD) experimental plan is adopted to evaluate the apparent shear strength of single-lap joint test (ASTM D1002-10). Then, for the more promising treatment conditions, fatigue tests are carried out according to the ASTM D3166-99 standards, and cycles to failure are adopted to quantify the treatments. In addition, mechanical surface treatment (sandpaper polishing) is adopted as a reference treatment. Findings demonstrate that laser treatments significantly enhance the fatigue life of the joints (up to six times), offering a promising alternative to traditional mechanical methods
A two-step full laser surface treatment to improve the adhesive bonding of aluminium-aluminium joints
Full text linkTo improve the adhesion between Aluminium-Aluminium joints, a two-step laser surface treatment was developed and tested, adopting a 30W pulsed Yb:YAG nanosecond laser source. The process consists of a first phase, called laser texturing, where a deep texture is obtained on the adherents by adopting high pulse energy and several repetitions, followed by a further laser treatment, called laser cleaning, carried out with lower energy content, and applied over the overall adhesion surface. To characterise the treatment process, the effects of technological parameters on texturing geometry were first investigated to select the proper texture; then, textures with different selected geometries were carried out and adopted to produce single-lap joints according to the ASTM D1002-10 Standard. An epoxy system adhesive was adopted for the joining. Furthermore, samples with only one-step treatment (i.e. only laser texturing or laser cleaning), standard treatment (sandpaper), and acetone cleaning were fabricated and adopted as reference samples. Analysis of variance was applied to study the effect of the process parameters, and digital image analysis was adopted to evaluate the percentage of adhesive/cohesive failure. From the results, compared to the only textured reference samples, the two-step laser treatment increases the apparent shear stress regardless of the adopted texture geometry. Moreover, it was found that only laser cleaning treatment can significantly improve joint strength compared to the untreated sample
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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