1,721,048 research outputs found
CO2 laser polishing of laser-powder bed fusion produced AlSi10Mg parts
No full textPoor surface quality represents an important issue that needs improvement for metal Additively Manufactured parts. Both short or long wavelength lasers have been applied for surface polishing in order to improve the surface finish. In this work, the possible use of a CO2 laser for the surface polishing of AlSi10Mg parts made by Laser-based Powder Bed Fusion (L-PBF) was explored. The high surface roughness in the as-built condition can lead to increased laser energy absorption. In order to assess the effects of the main laser-related process parameters, the experiments were carried out on L-PBF samples built vertically with respect to the build platform. Their effect on the surface were evaluated by means of the surface arithmetical mean height (Sa), surface skewness (Ssk) and primary profile root mean square slope (Pdq), obtained via confocal microscopy. Microstructure evolution was also investigated by means of SEM and EDS analysis. The results showed a large reduction in surface roughness, ranging from the 67% to the 85% of the starting value. Microstructure of the re-molten layer revealed an increased grain size and an increased Si content that led to an overall hardness increase from 85 to 121 HV
Xps, sem, dsc and nanoindentation characterization of silver nanoparticle-coated biopolymer pellets
No full textThe development of environmentally friendly materials has been the focus of many research groups in recent years due to increased harmful effects of plastics on the environment. Bio-based materials are considered a key solution from a sustainable manufacturing perspective. The nano-coating of biopolymer blends with silver nanoparticles is the subject of challenging research projects in line with the EU Directive on environment protection and sustainable manufacturing. Coating biopolymers with silver nanoparticles provides an antimicrobial and antiviral active surface. In this work, we develop silver nanoparticle-coated biopolymer Arboblend V2 Nature pellets. The main goal is to obtain a new material with antibacterial action obtained from the blending of a biopolymer pellets with silver nanoparticles through physical vapor deposition. The study is divided in three steps. The first step represents the silver nano-coating of the Arboblend V2 Nature and the characterization of the coated/raw pellets. The second step involves the injection molding of the silver nano-coated pellets and the characterization of the samples obtained. The last step regards the press molding of the coated pellets in order to obtain thin films, as well as their characterization. The PVD-sputtering technique is used to coat the pellets with silver nanoparticles. This process is especially optimized for coating raw materials with high water content and small-size pellets. The mechanical properties, surface chemical composition and the thermal properties of the both virgin and silver nanoparticle-coated biopolymer pellets are measured and analyzed for mechanical and thermal resistance of the nano-coating layer. Differential scanning calorimetry, scanning electron microscopy, X-ray photoemission spectroscopy and nanoindentation mechanical testing is performed. The calorimetry test detects no significant alteration of the biopolymer produced from the PVD process and confirms the optimized PVD process for nano-coating of the Arboblend V2 Nature pellets with a viable application in nano-silver–biopolymer composite products
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
Investigation of compression behavior of PE/EVA foam injection molded parts
No full textThe main objective of the presented work is to evaluate the compression behavior of a polymeric foam blend by using a robust framework for the testing sequence of foaming injection molded parts, with the aim of establishing a standard testing cycle for the evaluation of new matrix material. The research purpose is to assess parameters influencing compression behavior and give useful suggestions for the implementation of a finite element analysis. The polymeric blend consisted of a mixture of low density polyethylenes (LDPEs), a high- density polyethylene (HDPE), an ethylenevinyl acetate (EVA) and an azodicarbonamide (ADC). The thermal, rheological and compression properties of the blend are fully described, as well as the injection molding process for two specimen types
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
Comparing the adhesion strength of 316L stainless steel joints after laser surface texturing by CO2 and fiber lasers
Full text linkThis paper focuses on the effects of the laser surface texturing process and joint configuration of stainless steel adherends on the adhesive tensile bond strength. Two different sources, a CO2 and a fiber laser, were used and compared. In particular, proper choice of laser parameters was explored with the aim of producing different roughness and peak-to-valley distance and different textures on the bonding area, which could increase the real contact surface. Furthermore, to more thoroughly understand the effect of the laser parameters on joint fracture load, the experimental campaign was conducted according to a Design of Experiment (DoE) framework and the results were analyzed with this methodology. The creation of particular textures and roughness levels were related to the resulting joint geometrical configuration and bond strengths. In particular, significant increases in joint bond strength were achieved using both laser sources. Furthermore, by optimizing the laser parameters, smaller laser spot scan path overlaps can be achieved as well as a more refined scale of surface texture and surface roughness. This thereby enables the joining of thinner sections of different materials
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
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