1,721,056 research outputs found
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
Morphological and fracture studies of alloys of thermosets and thermoplastics.
No full textTo improve the fracture toughness of brittle epoxies, the incorporation of various thermoplastics was studied. These materials exhibited multiphase structures, which were found to have significant influences on effective toughening. Initially, simple epoxy/polyethersulfone (PES) systems were investigated. The objective was to establish the relationships (1) between PES chemical structures and the resultant morphologies and (2) between these morphologies and fracture toughness. Modification of the chemical structures included variations of the end groups and the molecular weight. The effects of the concentration of PES and the processing conditions were also evaluated. All variables showed significant effects on the structural development, resulting in a wide range of multiphase microstructures. Despite the various morphologies, only the inverted phase structure coupled with the weak interface exhibited substantial fracture toughness improvement. Debonding and microcracking at the interface prior to the main crack were observed. Additionally, plastic deformation of the continuous phase, which was mainly comprised of ductile PES, was confirmed. Fracture analysis revealed that microcracking was effective only to relieve triaxial stress state ahead of the crack tip, and the major contribution to toughening seemed to be attributed to the yielding of the ductile continuous phase. Next, phase separation and the structural development of the epoxy/PES systems were examined theoretically and experimentally. Although phase separation was proven to be a natural consequence of the Flory-Huggins theory, this theory does not account for the effect of the end groups and the processing conditions. Finally, amorphous-crystalline block copolymers were evaluated as novel toughening agents. These materials, which incorporated crystalline phases in the epoxy matrix, utilized an alternative toughening mechanism, namely phase transformation toughening. Our experimental results confirmed that polybutyleneterephthalate (PBT) segments of the copolymers could form either closely packed crystal lamellae or finely dispersed single lamella. The crystallization behavior of the PBT segments was found to be greatly constrained by the epoxy network as well as the PES segments. Several characteristic morphologies were obtained upon failure, however, improvement in fracture toughness was marginal.PhDMacromolecular Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104648/1/9542885.pdfDescription of 9542885.pdf : Restricted to UM users only
Fundamental molecular mechanisms of moisture transport in epoxy.
No full textThe epoxy resins used in high performance aerospace composites typically absorb significant quantities of water, compromising the physical properties of the component. In this research, the ill-defined contributions of molecular topology to the moisture transport process are examined. Topology refers to the spatial arrangement, or packing, of the molecular segments within the epoxy. By combining this understanding with the known contributions from resin polarity, a molecular model of transport is proposed to provide scientists with the knowledge needed to create moisture-resistant epoxies and composites. Positron annihilation lifetime spectroscopy (PALS) quantifies the amorphous topology in terms of the size and volume fraction of nanometer-sized voids. Through novel epoxy networks, the topology is systematically altered while the polarity is held constant. For the transport studies, the subsequent nano-pores comprise 3 to 7 volume percent of the epoxy, with radii of 2.5 to 3.1 A (water has a radius of 1.3 A). Extrapolation of the PALS data to absolute zero identifies the intrinsic hole volume fraction, with approximately 1/5 to 3/5 of the nano-pores ascribed to the intrinsic component. The PALS nano-pores are a local measure of the molecular packing and furnish information not afforded by macroscopic parameters, such as specific volume. A limited number of correlations exist between the transport properties and the nano-pore characteristics. Both the equilibrium moisture uptake and the initial absorption rate (initial flux) increase with the intrinsic hole volume fraction. The diffusion coefficient exhibits a mild exponential dependence on the average nano-pore size, but only at low temperatures. As a general rule, these correlations between transport and topology, as quantified in the dry resin, are strongest under conditions where the moisture is ineffective at altering topology, such as low temperatures and the initial stages of absorption. A molecular model of the moisture transport process is proposed. Water appears to traverse the epoxy through the nano-pores, which establish dynamic, interconnected pathways of unoccupied volume. The nano-pores effectively open the matrix and provide access to the polar hydroxyls and amines. These interactions between water and the polar sites ultimately dictate both the rate and amount of moisture absorbed.PhDApplied SciencesMaterials sciencePolymer chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131542/2/9909996.pd
Recommended from our members
Mechanical performance, stability, and antimicrobial efficacy of a polymer surface with biomimetic nanopillars
Get PDFContact lenses contaminated by pathogenic fungi and bacteria cause eye infections, resulting in ~1 million doctor’s office visits every year, at a cost of $175 million annually in the USA alone. The most severe of these infections are plagued by protective biofilm, which make the microbes more tolerant to current drug therapies, and creates an urgent need for alternative strategies. In my thesis research, material and topographical solutions inspired by nature are explored. I investigated the use of the biopolymer chitosan, which is antimicrobial, biocompatible, plentiful, and inexpensive. The anti-biofouling surface structures found on cicada wings, shark skin, and fish scales are used as inspiration for nanopillars imprinted on chitosan. The fabricated surfaces can prevent biofouling and influence the mechanical performance of the material.The specific goals of this dissertation are to: 1) Fabricate, characterize, and optimize the design of a chitosan hydrogel film with nanopillars which remain stabilize even after immersion in liquid; 2) Evaluate the antimicrobial efficacy of the chitosan hydrogels with nanopillars against Fusarium oxysporum and Pseudomonas aeruginosa; and 3) Investigate the link between the mechanical performance and nanopillar surface on the chitosan hydrogels. I demonstrated in this thesis a scalable process to fabricate bioinspired nanopillar surface structures. The bioinspired surface generally enhances the antimicrobial efficacy and mechanical performance of several types of hydrogel films. The generalization of this technique has important implications and commercial potential
- …
