1,720,964 research outputs found
Nonlinear mechanical model of a fluid inerter
Full text linkDynamic vibration control devices provided with inertance, such as Tuned Inerter Dampers, Tuned Mass Damper Inerters or Tuned Liquid Column Damper Inerters, have been shown in numerous numerical studies to have superior vibration mitigation performance compared to conventional devices, such as Tuned Mass Dampers. One possible way to produce this inertance effect is by means of a moving fluid. In this study, the dynamic performance of such a fluid inerter is analyzed experimentally. The considered small-scale prototype consists of a hydraulic cylinder, and the inertance is generated by the flow of the working fluid in an external channel attached to the cylinder itself. In a first step, the dry configuration, i.e. without fluid, is investigated, revealing a nonlinear dissipation force. In a corresponding mechanical model, this force is represented by a variant of the well-known Stribeck effect. Subsequent experiments on the complete configuration, i.e. with fluid, reveal a further nonlinear effect. This effect is attributed to the compressibility of the working fluid as well as air trapped in the channel. Once the parameters of the mechanical model are retrieved, comparative studies are carried out. These show a remarkable agreement between numerical and experimental outcomes, thus enabling the mechanical model to be used in dynamic vibration control devices, as stated above
A variant design of Tuned Mass Damper Inerter for reducing displacements of base isolated structures
Full text linkIn this study an innovative passive control strategy, referred to as New Tuned Mass Damper Inerter (New TMDI), coupled with a base isolation system (BI), is presented with the aim of reducing displacements in base isolated structures subject to seismic actions.
The proposed New TMDI employs the synergetic benefits of a recently developed non-traditional Tuned Mass Damper (known as New TMD) and an inerter device to achieve higher control performances in isolated structures. Specifically, the New TMD is a secondary mass system connected to the BI system by a spring and to the ground by a dashpot. In addition, in the New TMDI configuration, the inerter device is placed in parallel with the damper.
The New TMDI optimal parameters are determined by performing a simplified approach which provides simple closed-form formulae as a quick tool to design the examined device. The reliability of the proposed approach is assessed by a comparison with a more accurate and computationally complex numerical optimization procedure. Further, the performance of a base-isolated multi-degree-of-freedom structure equipped with a New TMDI is investigated taking into account different recorded ground motions as base excitation. Results from time history analyses assess the mitigation effect due to the optimal New TMDI on the response of base-isolated structures, also in comparison with those of a conventional Tuned Mass Damper Inerter (TMDI). On this base, the proposed New TMDI might be considered as preventive conservation strategy for applications also in historic buildings, where general constraints require limited space for the base displacements
Experimental and numerical investigation of a fluid inerter for structural control
No full textIn the study presented here, the dynamic properties of a fluid inerter, including nonlinear effects, are characterized and the degree of its effectiveness in structural control is assessed. A fluid inerter is a mechanical device that models an element with unit of mass whose mass property (called inertance) greatly exceeds its physical mass. To this end, a small-scale prototype is realized and experimentally investigated. Linear and nonlinear parameters are identified to obtain a mechanical model suitable for more accurate parametric studies. Numerical simulations based on a finite element model are performed to evaluate the effects of the air unavoidably trapped in the system. In order to apply the device to engineering problems in more general configurations, a linearization procedure is performed for the nonlinear system elements and a comparison is made between the real and the linearized system
Fluid inerter-based vibration control of multi-modal structures subjected to vertical vibration
No full textThe so-called inerter is an attracting device that offers a solution to the goal of realizing or improving structural control devices with high mass ratios while avoiding the undesirable increase in dead load. The research presented here focuses on evaluating the performance of a fluid inerter in mitigating vertical vibrations of structures that exhibit multi-modal behavior, such as plates. First, a numerical study based on previous experimental data investigates the properties of the connection between the inerter and the structure to be controlled. Considering that a flexible connection has been shown to introduce a linearization effect, while a rigid connection of the inerter to the controlled structure can achieve significant displacement reductions, the influence of these two connection types over different inertance ratios is analyzed. To evaluate the practical suitability of the flexible connection to reduce the inherent nonlinear effects associated with the device, a novel application of the fluid inerter for vibration control in multi-modal structures is presented, exemplified by a cross-laminated timber panel, and compares its control performance with that of a conventional Tuned Mass Damper (TMD). This provides insight into the effectiveness of the inerter in controlling vertical vibrations. In addition, optimization procedures are employed to determine connection parameters that enhance the effectiveness of both the TMD and the inerter in mitigating vertical vibrations
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
- …
