1,720,967 research outputs found
STUDY OF A TRELLIS PYLON VIBRATIONS INDUCED BY WIND LOADS AND CONTROLLED TRHOUGH AN AMD
No full textThe rapid expansion of telecommunications infrastructure, driven by the deployment of the 5G network, necessitates innovative engineering solutions to ensure the reliability and stability of these critical structures. Steel trellis pylons, designed for hosting several telecommunication antennas, are particularly susceptible to wind-induced vibrations due to their slender profiles, high equivalent area exposed to wind loads and low structural damping. Such vibrations can lead to structural deterioration, signal disturbance, and, in severe cases, total structural failure. In this context, the need for effective vibration control measures is becoming more and more relevant. This paper underscores the complex challenge of wind-induced vibrations in telecommunications pylons and the promising potential of AMD systems as a mitigation strategy. This study aims at advancing the state of the art by integrating experimental wind load measurements, modal analysis, and the application of AMD technology to a 50-meter-high steel trellis pylon. Through comprehensive analysis and numerical simulation, the effectiveness of AMD systems in enhancing structural performance and resilience under wind loading conditions is validated
AN ACTIVE MASS DAMPER FOR VIBRATION CONTROL OF A SLENDER STEEL STRUCTURE
No full textThis paper describes the application of an Active Mass Damper (AMD) to control the vibrations of a steel truss tower placed on the top of a hill in Tuscany (central Italy). The device is manufactured with two linear motors that actuate two moving masses placed perpendicular to each other to independently control the components of the in-plane oscillation. First, a Finite Element Model (FEM) of the structure is developed and calibrated based on an Experimental Modal Analysis (EMA). The model is adopted at the design stage for dimensioning the AMD, based on the forces required to significantly improve the system structural damping. Then, the experimental results obtained in the field are reported for the structure subjected to wind loads, both with the AMD activated (controlled structure) and with the AMD switched off (uncontrolled structure). The improvements of the system dynamics introduced by the AMD is demonstrated in terms of damping increase and oscillation reduction when the structure is subjected to variable wind loads
Wireless sensor nodes for freight trains condition monitoring
No full textObjective of the present work is to present the design and the laboratory tests of Wireless Sensor Nodes (WSNs) equipped with three different on-board energy production systems, to be installed on freight trains for condition monitoring and structural diagnosis of the railway vehicle. The three sensor nodes are designed to be completely energetically autonomous, exploiting three different energy sources easily available on a moving train: Solar, Wind and Mechanical vibration power. a PCB board hosts different ICs, able to convert the uncontrolled and unregulated power sources in order to properly feed all the on-board components and possibly to charge the battery. The electronics for the acquisition, elaboration and wireless transmission of data, is presented and analyzed in terms of performances and consumptions. The three WSNs, based on the different energy sources, are designed and compared in terms of fatigue behavior and performances by means of laboratory tests
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
Design and validation of a hardware-in-the-loop test bench for evaluating the performance of an active mass damper
Full text linkThe purpose of this study is to propose an innovative solution for evaluating the performance of a full-scale Active Mass Damper (AMD). The AMD adopted is a custom hydraulic actuator, developed for active control of existing buildings against earthquakes. For vibration control, a sky-hook algorithm was implemented. Its characteristics ensure good robustness, which is fundamental in structural engineering since buildings are subjected to significant variation in dynamic properties in presence of damage or ambient conditions. A Hardware-In-the-Loop (HIL) test bench was specifically designed to simulate the actual working condition of the anti-seismic system. The HIL setup consists of a shaking table moved by a hydraulic actuator in accordance with the roof's displacement, evaluated using a structural numerical model of the building to which the AMD is fixed. The presence of two distinct active systems (HIL and AMD) could generate control issues; therefore, a Triple Variable Control logic was introduced to reduce the interaction delay. The effectiveness of the proposed AMD is validated comparing the roof's displacement in an uncontrolled structure with that in a controlled one. Also, the robustness of the control algorithm was verified using a non-linear structural model and applying seismic excitation at different intensities
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
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