1,720,954 research outputs found
Computationally-efficient kinematics of an in-parallel actuated wrist
No full textThe knowledge of machines’ kinematics is the first and fundamental step for their study and many different tools and approaches are available to the researcher or the technician to work out a mathematical model. However when machine’s kinematics must be solved and implemented in some programming language for the real-time control of the machine, it is important that the developed model is computationally efficient and written on fast rate hardware.
This is actually the case encountered by the researchers of the Polytechnic University of Marche; in fact they had to realize the control of a spherical orienting device which is available in the Laboratory of the Department of Mechanics and is in-parallel actuated by three linear motors: the performances of such machine were potentially very good but a first implementation of the controller, developed by means of the Flexmotion card on the NI/PXI platform, put in evidence the need of a boost in the evaluation times of kinematics loops.
To this aim the Authors pursued a twofold strategy: looking for a more efficient way of deriving the kinematic model of the machine and implementing it on high-rate control hardware.
In the last years many researches focused their attention on the computational problems related to solving the complex kinematics of PKM’s. Since 1990, for instance, Innocenti and Parenti-Castelli [1] introduced a new efficient way of solving the direct kinematics of Gough-Stewart based machines, taking advantage of the polynomial nature of the problem. Many researchers in the following years improved their approach and specialized it to different specific cases and in the present work the Authors applied the method to work out the solution of the kinematics of the mentioned spherical parallel machine.
The resulting model is very compact and allowed an easy implementation on a control card based on the FPGA (Field Programmable Gate Array) architecture. The main characteristics of such device are the flexibility, that makes it fully reprogrammable and suitable for the realization of logic functions, and its implicit parallel architecture that ensures high-speed computation capabilities, thus making it particularly suitable for real-time applications [2]. Nevertheless, it is important to remark that the implementation of FPGA based algorithms requires a fixed-point arithmetic representation and therefore a particular care in software development.
Finally, the Authors are presently developing a simplified model of machines’ inverse dynamics in view of the development of model based control laws: in this case the compactness of the model is obtained through the application of the principle of virtual work [3] and the use of screw theory [4] to simplify the formulation of the differential kinematics
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
Modelling and control of a spherical robotic device
Get PDFThe researchers at the Polytechnic University of Marche developed a spherical parallel manipulator designed for the orientation of parts or tools: the paper presents the first experimental results on such innovative machine. A model of the prototype robot has been realised by means of commercial multibody software then both open-loop and closed loop dynamics has been studied. The relative simplicity of machine kinematics allowed also to experiment the use of controllers with compensation of gravitational terms
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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