1,720,966 research outputs found
Sintesi funzionale, progetto e realizzazione di micromeccanismi cedevoli ad attuatori remoti per applicazioni endoscopiche
No full textSono illustrate alcune fasi del progetto e delle realizzazione di un micromanipolatore parallelo cedevole, con attuazione remota, da dedicare ad applicazioni endoscopiche. E’, dapprima, introdotto il metodo di analisi del modello detto pseudo-corpo-rigido, giustificandone alcuni criteri di definizione, in base al comportamento delle aste a semplice curvatura, inflesse. Sono proposte due applicazioni del modello pseudo-corpo-rigido dedicate l’una allo studio dello spazio di lavoro ad orientamento costante della piattaforma, l’altra alla sintesi del manipolatore per assegnate rotazioni della piattaforma mobile. Infine, le configurazioni deformate della struttura realizzata, sottoposta all’azione di differenti insiemi di forze ridondanti, sono confrontate con le corrispondenti deformate ottenute con un programma di analisi agli elementi finiti
Micro Compliant Spatial Platforms for Optical Fibre Guidance Operations
No full textIn this work some novel kinematic structures of micro-compliant spatial manipulators are presented. The systems are analyzed both experimentally and by means of a predictive model based on finite element analysis. The comparisons between the FEM models and the prototypes have shown that, at the state of the art, the deformations of this class of micro manipulators can be studied conveniently by FEM analysis. Among the 4 structures presented the latter, very similar in spirit to a well known parallel manipulator, seem to be the most promising in terms of mobility for the guided platform
The Development of an Experimental Apparatus for testing Hybrid Lubrication in Spherical Bearings: numerical simulation
No full textThis investigation is dedicated to the solution of the indirect problem in a spherical pad lubricated under the condition of hydrodynamic regime, with externally pressurized inlets. The work has been motivated by a recent project which involves the development of an infinite ratio Continuously Variable Transmission (CVT) based on the adoption of a train of rotating spheres placed among two toroidal cones. The real feasibility of this system relies on the efficiency of two lubricated spherical pairs. Although the angular velocities are supposed to be relatively high, the spinning balls may be subject to loads which push them against their sockets. For this reason, it is necessary to deeply understand if a hybrid lubrication strategy might be able to avoid direct contacts and cavitation, specially at high loads or during transients with small velocities. The preliminary numerical simulation has pointed out how hydrodynamic lubrication is more effective when the eccentricity has a component perpendicular both to the load and to the rotation axis
An Experimental Investigation on Positioning Control of a Compliant Micro-Manipulator
No full textIn this paper, the angular position of the end-effector of a tendon-driven micro-manipulator has been experimentally controlled. In particular: a) the prototype of a 6 D.O.F.’s in-parallel micro platform has been built; b) the corresponding 3D model has been created and analyzed throughout the finite elements analysis; c) the platform angular positions of the 3D model have been evaluated for an assigned set of the 6 actuating forces; d) a control and data acquisition system, based on real time FPGA platform, has been configured and calibrated; e) the prototype platform has been moved by imposing a series of angular positions as the one detected by the FEA, for the same sets of externally applied loads; f) the predicted and the experimental trajectories have been compared, and their good correspondence has confirmed the feasibility of FEA as provisional model for this kind of micro-systems
Direct Coupling of Robotic Hands or Prostheses with the Radius Ulna Complex
No full textA new method of mechanically connecting artificial or robotic hands to the human arm is herein described. The idea is based on techniques which make use of fracture fixation devices, very well known in orthopedics. The presented connecting system consists in a real 3 DOF (w.r.t. the humerus) mechanism that has two end plates which are fixed directly, one on the radius, on the ulna the other. Since the system is a new concept project, no data exists about its reliability. Therefore, in the paper, a feasibility study on the most delicate components is described. In particular, FEA has been performed on the screws and on the bone-nut-screws, and some experimental tests in vitro have been made on a pig rib
Cerniera a cedevolezza selettiva - Selective Compliance Hinge
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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
Variations 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
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