1,721,061 research outputs found
Optimizing crystallinity of engineered poly(lactic acid)/poly(butylene succinate) blends: The role of single and multiple nucleating agents
No full textThis work deals with the design and experimental development of formulations based on bioplastic materials optimized for the production processes of high-performance packaging products, suitable for food contact and characterized by high thermo-mechanical stability. For this purpose, mixtures of poly (L-lactic acid) (PLLA)/poly (butylene succinate) (PBS) (PLA/PBS) containing micro-lamellar talc as reinforcing agent and inorganic nucleating agent have been obtained on a pre-industrial scale. Through the addition in formulation of two organic nucleating agents, ethylene (bis)stereamide (EBS) and poly (D-lactic acid) (PDLA), evaluated separately and in combination with each other, four different PLA/PBS formulations were produced by means of a co-rotating twin screw extruder. The effects on the crystallinity of the materials obtained first in the form of pre-dried pellets, then in the form of films by casting extrusion and, finally, as thermoformed items were compared, according to the variation of the chosen nucleation system. The effect on the crystallinity of the materials was assessed by differential scanning calorimetry (DSC) and by Fourier transform infrared analysis in attenuated total reflection mode (ATR-FTIR). This approach aims to provide data for the further investigation on the processability and the thermo-mechanical properties of end-goods achievable by converting processes (melt processing) of the bioplastic compounds
Dissimilar joining of transparent poly(ethylene terephthalate) to aluminum 7075 sheets using a diode laser
No full textLaser welding has improved the manufacturing productivity and made a great opportunity over conventional joining methods. Producing hybrid metal-polymer components is drawing more attention in terms of their aptitude specifically in the aerospace and automotive industries. The joining of a hybrid metal and a polymer can be troublesome due to some drawbacks in chemical and physical properties or incompatible structures. Diverse techniques are applied for joining dissimilar materials, specifically polymers and metals with the purpose of achieving high flexibility. Laser welding is an effective technology to join dissimilar materials with considerable advantages such as flexibility, low environmental impacts, noncontact, high speed, and accuracy. In fact, the main challenge for manufacturers is still on how to choose the input process parameters to get the best joint performance. This paper investigates an experimental study of dissimilar welding of transparent Poly(ethylene terephthalate) to aluminum 7075 sheets by a diode laser. Laser joining parameters play a crucial role in determining the quality of joining between PET films and aluminum plates. In the present work, laser power and scan speed were considered as operational parameters, which have a significant influence on the quality of the joint zone. Laser transmission joining was optimized using response methodology for achieving good joint strength with minimal barriers
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
L’identità professionale dello psicologo: competenze specifiche/capacità di orientarsi
No full textVariations 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
Design and manufacture of degradable polymers: Biocomposites of micro-lamellar talc and poly(lactic acid)
No full textOver the last decade, biopolymers have seen a sharp increase in their market share as an alternative to conventional oil-based plastic materials. Among them, degradable biopolymers are rarely employed, especially in the field of durable end-goods, because of their often limited chemical, mechanical and thermal behaviours. In contrast, stringent international regulations encourage the employment of low-impact materials in several manufacturing domains, with degradable polymers considered par excellence. In the present work, an innovative route to control the final properties of an extrusion-compounded, high-performance biocomposite composed of polylactic acid (PLA) reinforced with micro-lamellar talc is proposed. For this purpose, talc was first modified via surface reaction with organic (i.e., belonging to the class of polyisocyanates) or hybrid organic-inorganic (i.e., belonging to the class of organosilanes) compatibilizers, respectively. Custom-built formulations were then achieved by the dispersion of the pretreated micro-lamellar talc in commercial-grade PLA. The resulting compounds were analysed by differential scanning calorimetry (DSC) and attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. The experimental findings show that PLAs with different properties can be achieved as a result of chemical and physical interactions among the functional groups on the surface of the pretreated talc and the terminal groups of the PLA chains. These results are extremely promising for the achievement of innovative grades of PLAs suitable for melt processing and to ensure the greatly improved chemical inertness, thermal stability and mechanical strength of the resulting end-goods
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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