1,720,976 research outputs found
Ricerca sul tema "Investigations into electrostatically actuated nonlinear microbeams as components of ultra-fast switches"
No full textElectrostatically actuated beams are common elements in microelectromechanical devices that serve as high-frequency resonators,
actuators, and sensors. The present effort serves to develop a comprehensive nonlinear modeling paradigm for such device elements
that accounts for nonlinearities due to the electrostatic field, beam deformations, and intermittent mechanical contact. The presence
of these complex aspects associated with the force field, the inherent beam behavior and the interactions with rigid obstacles calls
for advanced modeling techniques that account for the finite configurational changes via geometrically exact approaches.
An immediate practical application is the design of highly sensitive limit switches for use as indicators or control devices in
micromechanical systems.
The limit switches considered here rely on an abrupt transition of the internal state of the switch between two distinctly different
steady-state behaviors as a result of a small change in the value of a system parameter. The present collaboration will explore a
limit-switch design that relies on the abrupt transition associated with the onset of low-velocity impacts between an electrostatically
actuated beam element and its environment. This is supported by theoretical predictions indicating a post-trigger response rate that
grows beyond all bounds as the threshold parameter value is approached. The proposed phenomenology thus compares favorably
with existing designs in terms of guaranteeing a more instantaneous switch response.
The proposed research is strongly driven by a combined effort from two complementary backgrounds, that in nonlinear continuum
mechanics of Prof. Lacarbonara and that in non-smooth system dynamics and bifurcation theory of Prof. Dankowicz. The outcome of
this collaboration is expected to be interesting and highly fruitful to both Institutions, the University of Rome La Sapienza and the
University of Illinois at Urbana-Champaign, from a transfer-of-knowledge perpective and from merely scientific and technological
stanpoints.
Further, the collaboration is already supported by an ongoing personnel exchange at the graduate student level
General-Purpose Finite Element-Based Path Following of Nonlinear Dynamical Systems
No full textThis paper summarizes ongoing efforts toward an advanced integration of algorithmsfrom the finite-element and bifurcation domains, thus enabling an accurate and effective unfoldingof the bifurcation and post-bifurcation scenarios of nonautonomous PDEs typical of nonlinearstructural dynamics including multi-physics applications. The developed tools rely on a nonlinearfinite-element (FE) formulation coupled with a MATLAB-based platform for continuation of periodicorbits called COCO.The paper demonstrates the versatility of the approach through a comparison between the predictionsof the frequency-response curves for a hinged-hinged nonlinear beam subject to a primaryresonanceharmonic transverse load using an in-house FE discretization of the approximate Mettlermodel and using a FE discretization of the special Cosserat model of rods implemented in COMSOLMultiphysics. As the latter accounts for the full nonlinearities and extensional/flexural/shearing deformations,it is expected to yield physically more realistic results. As demonstrated in this paper, italso allows for a straightforward analysis of different sets of boundary conditions without the needfor further simplifications or model reductions
A procedure to analyse and compare the sensitivity to geometrical parameter variations of one-dof mechanisms
No full textSensitivity analysis to geometrical parameter variations aims at assessing how small changes in a mechanism parameters, for instance due to tolerances and clearance, can alter its nominal motion. This issue is very important for the characterization of a mechanism and has been widely addressed in the literature, but it needs further investigations. The high number of parameters characterizing the problem and their mutual influence indeed make it difficult to assess the sensitivity from a global point of view. In this paper, a procedure is presented to characterize and evaluate the sensitivity of one-degree-of-freedom mechanisms. As an example, such a procedure is applied on two mechanisms which are the basis to design knee prosthetic devices. In this context, sensitivity analysis is important to understand how the motion generated by a prosthetic device can be influenced by small variations of its geometry or by small misalignments during the installation phase on the patient
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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