1,720,954 research outputs found
A MSD model for coupled analysis of pedestrian-footbridge dynamic interaction
Full text linkRecent footbridges are characterized by long span, light materials and increasing slenderness which make them more sensitive to dynamic forces induced by pedestrians. While walking, the pedestrian adapts his gait to the bridge motion and interacts with the structure. At contact points, the pedestrian transmits contact forces to the bridge that, in turn, imposes a set of displacements and velocities to the pedestrian's feet. The bridge response accounting for the human-structure interaction depends both on reliable estimates of expected loading scenarios and on the accuracy of the models representing pedestrians.This work presents a complete framework for the analysis of the human-structure dynamic interaction. To properly describe this phenomenon, the coupled equations of motion for the two mechanical systems are derived. To this aim the standard FE modeling of the structure is retained, while a new bipedal mass-spring-damper model is adopted for the pedestrian. The model is able to reproduce the sequence of single and double support phases typical of the human gait and is excited by both an equivalent bio-mechanical force and the motion at contact points with the bridge. The solution of the coupled formulation is based on a forced uncoupling of the equations, possibly associated to an iterative integration procedure. At each time instant the two systems are analyzed separately: the bridge subjected to vertical contact forces, the pedestrian to an imposed motion at his feet.The uncoupled strategy of solution is implemented into a research code. In the case study groups of pedestrians cross a lively footbridge, whose modal properties were experimentally identified. The numerical model was developed with ANSYS. To investigate the potential of the proposed approach, numerical analyses have addressed the effect on the bridge response of both the degree of synchronization and the spatial distribution of groups of nine pedestrians. The bridge vertical accelerations reach values out of the range of comfort and show an high dependency on these parameters. The effectiveness of the proposed approach of modeling and analysis is highlighted. (C) 2017 The Authors. Published by Elsevier Ltd
Simulation of human induced vibration of a lively footbridge
No full textIn the last years, the need for structures able to link the functional and aesthetic role has led to the design of new flexible footbridges. The low ratio between permanent and variable loads makes them more sensitive to dynamic loads, such as the forces transmitted by pedestrians. During the human walking, the pedestrian moves on a flexible structure adapting his gait to the bridge motion. The interaction between pedestrian and footbridge takes place at contact points, where the pedestrian transmits contact forces to the bridge that, in turn, imposes a set of displacements and velocities to the pedestrian’s feet. The description of the human being as a mechanical system allows for the derivation of the equation of motion of the bridge-pedestrian coupled system. In this work a previously developed bipedal pedestrian mass-spring-damper (MSD) model is adopted. The analytical formulation of the human-structure interaction, involving the derivation of the bridge-pedestrian coupled equations of motion, has been implemented in a numerical code, named INTER2.0. The bridge is modelled using a commercial FE code and its geometry is fully described. The code reads in input both the bridge structural matrices and the pedestrian dynamic properties needed to assembly the MSD matrices or the feet forces. The present contribution investigates the effect, on a lively footbridge response, of a few parameters: distance between pedestrians and pedestrians’ trajectory. The results due to groups of pedestrians walking along different eccentric trajectories have highlighted the relation between the bridge mode excited and the pedestrians’ position. As it was expected, the eccentric transit induces a torsional behavior. In addition, the spatial distribution affects the bridge response: the vertical accelerations rise if the longitudinal distance among pedestrians increases, although this trend is not linear with the distance
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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