1,720,978 research outputs found
Novel Functional Graphene and its Thermodynamic Interfacial Localization in Biphasic Polyolefin Systems for Advanced Lightweight Applications
No full textImplementation of multiple polymers represents a fast and cost-efficient method to bring additional functional attributes that are practically impossible without a highly capital-intensive synthesis of the product from a monomer. However, most polymer groups are thermodynamically immiscible, resulting in the material to devalue in performance.
The purpose of this research is to study the impact of a novel nanostructured carbon co-factor on the compatibility between Polyethylene (PE) and Polypropylene (PP), in a macro-micro biphasic polyolefin system, with PE representing the macro phase. An alternative and inexpensive Graphene Oxide (GO) modification is performed for synthesizing a novel functional graphene. Then, a thermodynamically driven mixing mechanism of the three components is proposed for selectively localizing the additive at the PE/PP interface. The focus is on improving the structural attributes of PE, increasing its industrial value, through the combined effect of micro phase PP and interface localized novel functional graphene.
The experimental results highlight the effectiveness of the GO modification process in recovering pure graphene structure and properties, in a cost-effective way. Moreover, the preferential localization of the highly exfoliated novel functional graphene at the biphasic system interface lowers PE/PP interfacial tension and viscosity mismatch. This increases phase compatibility and promotes a remarkably fine dispersion of the micro phase into the macro phase. Consequently, a significant thermo-mechanical performance enhancement is seen, with stiffness and toughness being greater than the ones of virgin PP, and strength and heat deformation resistance almost matching the neat PP ones. Lastly, PE non-isothermal crystallization kinetics are investigated to validate the experimental data. It is shown that the increase in material’s performance is in direct correlation with nucleation-controlled PE crystallization, induced by the synergistic combination of micro phase and novel functional graphene.
These findings will allow industries to replace their PP based materials with one that has a more abundant, simpler, cheaper, and yet performant PE as the major component, bringing a paradigm shift in the manufacturing of advanced lightweight polyolefin materials with tuned functionalities, suitable for emerging engineering applications.Ph.D
Novel Functional Graphene and its Thermodynamic Interfacial Localization in Biphasic Polyolefin Systems for Advanced Lightweight Applications
Get PDFImplementation of multiple polymers represents a fast and cost-efficient method to bring additional functional attributes that are practically impossible without a highly capital-intensive synthesis of the product from a monomer. However, most polymer groups are thermodynamically immiscible, resulting in the material to devalue in performance.
The purpose of this research is to study the impact of a novel nanostructured carbon co-factor on the compatibility between Polyethylene (PE) and Polypropylene (PP), in a macro-micro biphasic polyolefin system, with PE representing the macro phase. An alternative and inexpensive Graphene Oxide (GO) modification is performed for synthesizing a novel functional graphene. Then, a thermodynamically driven mixing mechanism of the three components is proposed for selectively localizing the additive at the PE/PP interface. The focus is on improving the structural attributes of PE, increasing its industrial value, through the combined effect of micro phase PP and interface localized novel functional graphene.
The experimental results highlight the effectiveness of the GO modification process in recovering pure graphene structure and properties, in a cost-effective way. Moreover, the preferential localization of the highly exfoliated novel functional graphene at the biphasic system interface lowers PE/PP interfacial tension and viscosity mismatch. This increases phase compatibility and promotes a remarkably fine dispersion of the micro phase into the macro phase. Consequently, a significant thermo-mechanical performance enhancement is seen, with stiffness and toughness being greater than the ones of virgin PP, and strength and heat deformation resistance almost matching the neat PP ones. Lastly, PE non-isothermal crystallization kinetics are investigated to validate the experimental data. It is shown that the increase in material’s performance is in direct correlation with nucleation-controlled PE crystallization, induced by the synergistic combination of micro phase and novel functional graphene.
These findings will allow industries to replace their PP based materials with one that has a more abundant, simpler, cheaper, and yet performant PE as the major component, bringing a paradigm shift in the manufacturing of advanced lightweight polyolefin materials with tuned functionalities, suitable for emerging engineering applications.Ph.D
Experimental Studies of Static Mixers and Twin Screw Extruders
No full textThe laminar flow field in a Kenics KM® static mixer and a Werner and Pfleiderer ZSK-30® twin screw extruder (TSE) has been studied using laser induced fluorescence (LIF) coupled with digital image analysis, particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The objective of this study was to observe the flow fields in these two devices, to determine their mixing capabilities qualitatively and quantitatively. Mixing in the static mixer was quantified by measurement of the number average striation thickness, variance of striation widths and interfacial area for elements with 90 degrees of twist. From flow visualisation and LDA measurements, transitions were observed in the flow where vortices developed above the first and second elements. These vortices did not appreciably enhance mixing after 4 to 5 elements with an aspect ratio (L/D) of 1.0. The velocity field measured over the first four elements (L/D = 1.5), captured the mixing nature of the static mixer, where flow was split at the leading edge and recombined at the trailing edge of the elements. Recirculations in the radial plane were observed where fluid flowed from the high-pressure side of the element forward out along the tube wall to the low-pressure side or suction side. The radial flow field required a development length to allow the flow to build in magnitude. The rate of deformation analysis on the flow field indicated that mixing efficiency would be increased if the first element had a larger helix angle. The highest rates of deformation were measured at the junctions between elements, and between the element and tube surfaces. The visualisations coupled with image analysis for the TSE demonstrated clearly that the mixing was enhanced by placing a reverse conveying element directly after the last set of kneading discs in the mixing section. The velocity results for the screw profile with extended first and last discs (geometry A) showed an increase in back flow and recirculations with increasing screw rotation. When a forward conveying element was used before and after the kneading discs (geometry B), higher radial and lower axial velocities were measured. The fluid in the direction of rotation and no back-mixing or recirculations in the flow were measured. Results of a 3D model for the simulation of flow in the kneading disc region and the PIV measurements were compared. Results for geometry A are in good qualitative agreement for low flow rates. Geometry B showed better agreement at higher flow rates compared to lower flow rates. The performance of the kneading discs were characterized based on the shear, elongation and the magnitude of the rate of deformation tensor within the measured flow fields. For the various cases of screw rotation speed, the largest rates of deformations (elongation and shear) were seen at the first and last disc of the kneading block where transitions occurred.Doctor of Philosophy (PhD
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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