1,720,970 research outputs found
Nanomechanics with electron beam: detection and control of motion
No full textThe study of nanomechanics using an electron beam has developed into an area of research, with recent works reporting on Brownian and ballistic motion detection, dynamic backaction,visualisation of sub-nm motion and mass sensing. It is important because the electron beam offers a platform for real-time observations of dynamics exhibited by nano- and microscale objects, with sub-nm scale displacement sensitivity and MHz bandwidth, as well as for controlling and characterising mechanical properties. In this study, I report the following yet unexplored aspects:• I have introduced a new technique for detecting and mapping the periodic motion of nano/microscale objects via cathodoluminescence, with nanometric displacement sensitivity and spatial resolution, and MHz bandwidth implemented in a modified scanning electron microscope. Its capability is demonstrated by detecting and mapping driven motion of nanomechanical cantilevers. The technique offers a noise equivalent displacement amplitude spectral density of 1 nm/√Hz.• I have observed the phenomenon of dependence of the frequency of oscillation of a cantilever on the presence of the electron beam. The repulsion between an electron beam and charge accumulated on a nanomechanical cantilever yields a stiffening that increases its resonance frequency, providing a mechanism for controlling resonators and sensing charge. For a cantilever of microscale length and nanoscale cross-section interacting with an electron beam, I observe a resonance shift on the order of 5% per nanocoulomb. The resonance frequency was expressed as a function of induced charge and electron beam parameters such as position, beam current and acceleration voltage. The model was tested experimentally by varying the current of an electron beam and its distance from the edge of grounded and isolated cantilevers.• Driving oscillations of a nanomechanical beam can lead to a bistable response related to the nonlinearity of the mechanical restoring force. I have observed for the first time that the nonlinear response of a nanowire and the regime of bistability can be controlled by the electron beam impinging on the oscillator. A nanowire that is fixed at both ends and driven to the nonlinear regime of bistable resonant oscillation was switched between its bistable states by changing the distance between a 10 kV, 1.3 nA electron beam and the nanowire. The control mechanism has been explained as a consequence of electronbeam-induced heating, leading to thermal expansion that affects stress in the nanowire, which controls its resonance frequency. Therefore, the electron beam can shift thenanowire's bistable resonance relative to a fixed frequency of driven oscillation, enabling it to switch between the bistable states.In summary this thesis reports on new ways for characterizing motion and controlling dynamics of nano- and microscale systems with electron beams
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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