1,720,959 research outputs found
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
Tribology of newly developed EAL versus water in hydropower turbine bearings
No full textThe increasing demand for more readily bio-degradable, renewable and non-toxic environmentally adaptive lubricants with a lower degree of bioaccumulation has escalated the investigation of water-based lubricants as the potential alternatives for conventional mineral-based oils. Water is an excellent environmentally adapted lubricant; however, it is a low viscous fluid and holds downsides of having corrosive nature and extremely low pressure-viscosity coefficient leading to insufficient load-carrying capacity. These shortcomings make pure water a poor choice for operations involving high load and low speed, for instance, within hydropower applications. Therefore, the choice of appropriate modifiers and additives is crucial to improve the viscosity, friction-reducing performance and anti-wear properties of water as a base lubricant. Appropriate selection and combination of bearing materials also significantly improve the tribological performance of the lubricants. In the presented work, tribological behavior of polyvinylpyrrolidone (PVP) and poly(sodium 4-styrenesulfonate) (PSS) thickening agents with water as a base fluid in the lubrication of pure UHMWPE and SCF reinforced UHMWPE bearing materials has been investigated individually under reciprocating tribometer. The results showed that both PVP and PSS are excellent viscosity modifiers. PVP exhibited excellent friction-reducing and anti-wear performance, while PSS revealed increased wear rates with an insignificant reduction of friction coefficients. This study aims to explore the potential for using newly developed water-based lubricants in the replacement of traditional mineral-based lubricants for hydropower turbine bearings
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
Development of 3D printable thermoplastic polymer composites for tribological applications
No full textThe growing interest in environmental sustainability aims to improve resource efficiency and minimize energy consumption throughout material manufacturing, usage, end-of-life handling, and recycling aspect. Energy loss due to friction and wear of materials is the major challenge in machine components. Therefore, reducing friction and improving wear resistance with an appropriate selection of surface materials is the most direct route to reducing energy loss via reduced frictional forces, which contributes directly to sustainable development in the field of tribology and machine components. In that regard, polymer-based materials (PBM) are widely used as load-carrying components, such as bearings in tribological applications. In recent years, additive manufacturing (AM), also known as 3D printing, has gained widespread interest in the functional prototyping of PBM. 3D printing of polymers enables time-efficient processing with weight reduction and energy savings, addressing the sustainable development goals (such as SDG 9, 11, and 12) associated with the manufacturing of engineering materials. Additionally, the ability of in-field fabrication at the time of need increases the potential implementation of decentralized manufacturing with AM, reducing the resource depletion related to logistics and transportation. Therefore, AM/3D printing of PBM holds significant potential to provide a major enhancement to the current manufacturing capabilities with environmental and economic benefits. Fused filament fabrication (FFF) is an extrusion-based 3D printing technique with increasing popularity for the manufacturing of thermoplastic polymers. The printing technique, processing parameters, material selection, part characteristics, and final application are some of the factors affecting the sustainability and performance of 3D printed PBM. It should be noted that surface finish and internal defects are two of the most important challenges within the FFF method. In addition, the requirement of high thermal processing conditions for high-performing thermoplastic matrices often complicates the processability in FFF. Therefore, this research project aims to identify and optimize the important printing parameters in the FFF method, and to understand the mechanism and formation of internal defects, bulk properties, and tribological performance of 3D printed PBM. Initially, the key process parameters affecting the quality of 3D printed PBM are identified by employing commercially available filaments. The interrelationship between processing-induced defects and their impact on the material properties is explored. Moreover, novel polymeric composite filaments based on the polyether-ether-ketone (PEEK) matrix are developed in-house. Composite filaments are printed and evaluated as load-bearing components. To develop in-house self-lubricating filaments, microscale short carbon fibers (SCF) and nanoscale silicon dioxide (SiO2) particles are incorporated with the PEEK matrix using melt compounding and fabricated with FFF 3D printing. 3D printed parts are evaluated for their thermal, mechanical, and tribological performance. The characteristics of internal porosity and their impact on the material properties of these composites are investigated in this thesis. 3D printed PBM are examined using fractography and tomography to identify the impact of printing parameters on the bulk structure. Raster angle orientation and printing speeds impacted the location and shape of internal voids. Filament fillers were distributed along the material deposition path during the printing process. Adding micro-SCF in the PEEK matrix negatively influenced the formation of voids and interlayer adhesion, while nano-SiO2 improved the fiber-matrix interfacial bonding, reducing the internal porosity. Moreover, the mechanical properties of 3D printed composites significantly increased compared to neat PEEK. Similarly, the crystallization behavior and thermal decomposition temperatures of PEEK were positively influenced by the presence of fillers. Furthermore, 3D printed components were compared with conventional injection/compression molded samples, and the results showed similar tribological performance for both processing methods. The experimentally developed self-lubricating PEEK-based composites exhibited significant improvement in friction reduction and wear resistance compared to commercially available filament options. The multiscale composites showed superior tribological performance in dry sliding, exhibiting up to 50% friction reduction and reduction of specific wear rates by an order of magnitude (at 10-7 mm3/Nm) compared to printed neat PEEK. Analysis of wear mechanisms indicated that neat PEEK and SCF‑PEEK suffered severe abrasion and fiber-matrix debonding with increasing contact pressures, respectively. On the contrary, SiO2-SCF-PEEK composites showed improved wear resistance with smoother surfaces due to the polishing effect of nanoparticles and enhanced stress transfer from the matrix to reinforcements. The increased tribo-contact area with a larger polymer sample size adversely impacted friction characteristics with stick-slip, however, the effect on specific wear rates remains remarkably low. Water lubrication effectively improved tribological performance by reducing running-in duration and fluctuations during the evolution of friction coefficients. In this thesis, 3D printed self-lubricating PEEK composites were successfully fabricated and exhibited comparable friction coefficients and wear resistance to their corresponding compression-molded composites. The findings are evidence that FFF 3D printing can be explored as an alternative technique for the sustainable manufacturing of PEEK-based materials for tribological applications
Development of 3D printable thermoplastic polymer composites for tribological applications
No full textAppropriate 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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