1,720,956 research outputs found
THEORETICAL AND EXPERIMENTAL INVESTIGATION ON NOVEL NONLINEAR SUSPENSION BASED ON ORIGAMI METASTRUCTURE CONCEPT
No full textOrigami-type mechanical devices, initially designed for aerospace purposes due to their lightweight and foldable characteristics, exhibit unique nonlinear stiffness. Particularly, when suitably designed, they show Quasi-Zero Stiffness (QZS) characteristics within a specific performing range. The QZS property, aligned with the High Static Low Dynamic (HSLD) stiffness concept, brings an ideal passive vibration isolator to applications, especially for low-frequency vibrations. In this study, the vibration isolation capabilities of Origami-inspired suspensions, focusing on their viability as low-frequency passive vibration isolators, is investigated. Kresling Origami Module (KOM), stemmed from the compact design and compatibility with 3D printing technologies, is chosen. The investigation included a detailed analysis using 3D CAD, Finite Element Analysis, and experimental testing. The influence of geometric parameters on the nonlinear Force-Displacement curve is explored. Low-frequency isolation properties are confirmed by multibody simulations within the QZS region, but differences are recognized in dynamic properties beyond this range. The research underscored the transformative potential of Origami-type metamaterials in improving low-frequency vibration isolation technology. Challenges related to material properties and loading mass variations are discussed, providing valuable insights for future developments in this promising domain
Nonlinear dynamic behavior of spiral bevel gear by considering the torsional shaft stiffness
No full textSpiral bevel gears (SBGs) play a crucial role in developing silent power transmissions for non-parallel shaft applications, offering advantages such as improved motor allocation flexibility and space reduction. While SBGs have been recognized for reducing vibration magnitude in high-speed gearboxes compared to straight bevel gears, complete vibration suppression remains elusive, leading to potential challenges such as teeth contact loss and complex dynamic scenarios. To construct the dynamical model of SBG, time-dependent mesh stiffness and non-smooth nonlinearity caused by backlash is considered. The employed dynamical system is a three-degree-of-freedom model, integrating rotational shaft stiffness, to investigate the dynamic behavior of SBGs. Through the utilization of various analysis tools such as bifurcation diagram, Fourier spectrum, 3D-phase diagram, Poincaré map, and amplitude-frequency diagram are generated, revealing the presence of periodic, quasiperiodic, and chaotic responses in specific regimes. This research provides an in-deep understanding of the dynamic behavior of SBG system, contributing to the characterization and prediction of nonlinear phenomena, which is vital for the optimization and design of gear mechanisms across various engineering applications.Spiral bevel gears (SBGs) play a crucial role in developing silent power transmissions for non-parallel shaft applications, offering advantages such as improved motor allocation flexibility and space reduction. While SBGs have been recognized for reducing vibration magnitude in high-speed gearboxes compared to straight bevel gears, complete vibration suppression remains elusive, leading to potential challenges such as teeth contact loss and complex dynamic scenarios. To construct the dynamical model of SBG, time-dependent mesh stiffness and non-smooth nonlinearity caused by backlash is considered. The employed dynamical system is a three-degree-of-freedom model, integrating rotational shaft stiffness, to investigate the dynamic behavior of SBGs. Through the utilization of various analysis tools such as bifurcation diagram, Fourier spectrum, 3D-phase diagram, Poincaré map, and amplitude-frequency diagram are generated, revealing the presence of periodic, quasiperiodic, and chaotic responses in specific regimes. This research provides an in-deep understanding of the dynamic behavior of SBG system, contributing to the characterization and prediction of nonlinear phenomena, which is vital for the optimization and design of gear mechanisms across various engineering applications
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
SPIRAL BEVEL GEAR: THE NONLINEAR ANALYSES OF THE MESH STIFFNESS
No full textSpiral Bevel Gears (SBG) are key components of power transmission systems, where it is required to transfer power between intersected shafts. Understanding the dynamics of the system necessitates identifying the main sources of nonlinearity and time dependency. In addition to bearings and backlash, mesh stiffness is the parameter that introduces not only nonlinearity but also time dependency into the dynamical model. The time dependency mainly stems from the number of mated teeth, and the nonlinearity arises from the Hertzian effect. The transmission system undergoes different vibration levels; consequently, the gear pairs operate under varying load conditions, influencing the dynamic behavior of the system. Indeed, the dynamic mesh torque (DMT) on the SBG-pair teeth varies due to system vibrations, even though a constant input torque is assumed. Due to the complex geometry of the SBG, many studies on the vibration of the transmission system have considered a linear function for the torque and torsional deflection curve. However, this is not an accurate assumption due to the Hertzian effect. In the present study, a thorough analysis is carried out to propose an approach for obtaining mesh stiffness at different vibration levels. The accuracy of the proposed method is validated with verified results extracted from Finite Element Analysis (FEA). Analyzing the force-deflection curve reveals two different working ranges: normal, and high torque ranges. The normal torque range is where nonlinearity plays a significant role in the mesh stiffness, while the latter working range shows less nonlinearity. A comparison is carried out to represent dynamically the difference between average mesh stiffness, where a linear function is considered, and adaptive mesh stiffness, where a smooth function is considered for the force-deflection curve
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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