1,720,956 research outputs found
Improving the performance of profiled grinding wheels with a novel surface texturing robot
No full textThis work explores the improvement of a profile grinding process by creating grooves on the surface of a grinding wheel. Grooved grinding wheels have been shown by many authors to reduce the process forces, process temperatures and specific energy of the grooving process, thereby allowing higher grinding productivity. However, the use of grooved grinding wheels has never been explored for profile grinding applications, which differ in several ways from flat grinding processes. The main objectives of this work are to (1) investigate the state-of-the-art of grinding wheel grooving methods; (2) design, build and validate a method to produce helical grooves on profile grinding wheels; and (3) demonstrate the effects of helical grooves on the performance of a profile grinding operation and compare the performance to a conventional profile grinding wheel. An in-depth review of grinding wheel grooving technology literature was conducted. Using information from the literature review, a device capable of grooving grinding wheels was designed, built and validated. This device was found to be capable of producing groove geometries to within an accuracy of +/-10 micrometers. To achieve the desired accuracy, a novel kinematic error compensation method was developed as a part of the design of the grooving device. The device was then used to groove a profile grinding wheel. A grooved profile grinding process was found to have a 50% lower specific energy than a non-grooved process and significantly lower process forces. Furthermore, the grooved profile grinding wheel was capable of taking a depth of cut four times deeper than a non-grooved profile grinding wheel before process failure occurred. The grooved profile grinding wheel was found to produce a surface roughness approximately 80% larger than the non-grooved profile grinding wheel
Tethered Magnetic Serial Robots for Minimally Invasive Neurosurgery
Get PDFThe high-speed, non-ionizing, wireless power transfer capabilities of low-frequency magnetic fields make them an attractive option for actuating devices on the nanometer scale up to the centimeter scale, enabling a new suite of minimally-invasive techniques for a wide variety of medical procedures. There is a significant demand for smaller, more manoeuvrable, surgical robot tools to reduce the invasiveness of neurosurgical procedures. A magnetic approach to surgical robots could enable smaller tools, but no viable magnetic robot approach exists. Existing magnetic approaches to surgical tasks involve either untethered agents, serial arms with bulky surface-mount transmission units, or highly-underactuated continuum bodies. Surgical tasks, especially in delicate regions such as the brain, require precisely controlled trajectories and applied forces: they require fully-actuated robots.In this thesis, rigid-link serial robots with embedded magnets in each link are designed to achieve high forces and ensure full actuation over their configuration space. A novel analytical model was derived from a combination of magnetostatics and rigid-link serial robot dynamics to determine the equivalent actuator torques at the joints of the serial robot for a given actuating field, as well as the effective torsion-spring-like behaviour induced by interactions between the magnets in the serial robot. From this analytical model, a performance metric and novel design methodology was developed to improve the actuation performance and tailor the magnetic torsion-spring behaviour in the robot by adjusting the orientation and position of the embedded magnetic material. Several 3 mm - 4 mm diameter rigid-link robot prototypes were developed using this methodology, and their performance was evaluated according to key design criteria for microneurosurgical tasks. The tools can be operated open loop or closed loop with computer vision feedback, achieving step response rise times of less than 1 second and maximum output forces of up to 181 mN.
By enabling smaller tools without a need for transmission components, more space is left in the trocar (surgical insertion point) for other systems, such as lighting, irrigation, or integrated sensing. Magnetic serial robots could thus enable a new class of multifunctional surgical tools.Ph.D
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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