1,721,275 research outputs found
Monitoring seismic damage via Accelerometer data alone using Volterra series and genetic algorithm
No full textAn application of Volterra series in nonlinear system identification is presented in this paper. This novel approach makes use of accelerometer data alone. The aim is to develop an algorithm that can rapidly detect damage, caused by earthquakes, in infrastructural systems without the need for a parallel transducer system that also monitors relative displacements around predicted damage locations. In addition, this algorithm (here termed Method A ‘Acceleration only’) is shown to be effective for low to high levels of damage. It first extracts the estimated multimodal linear kernel using a genetic algorithm applied to the input/output structural acceleration time-series. This enables a very precise estimate of linear system parameters. It then subsequently extracts quadratic and cubic nonlinear (kernel) terms by making use of multinomial combinations of the wavelet basis of the input signal. Extracted nonlinear kernel acceleration time-series and their standardised cumulative norms are compared with normalised hysteretic dissipated energy which requires both response accelerations and displacements, (here termed method A/D “Accelerations and displacements’). As a heuristic case we investigate the performance of both method A, and method A/D in predicting probable damage in a Bouc-Wen nonlinear system. Results suggest that method A/D and method A are comparable at estimating the likely maximum system ductility. We develop a fragility curve for estimating the probability of damage based on our nonlinear Volterra series intensity measure. Finally, we verify the application of this Volterra series approach against experimental test data from physical laboratory shake-table experiments of reinforced concrete columns and demonstrate that this approach is useable in practice
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
Lateral dynamic bridge deck-pier interaction for ultra-high-speed Hyperloop train loading
No full textThe next generation of ultra-high-speed (UHS) trains, known as Hyperloop and TransPod, are aerospace type vehicles designed to carry passengers. The UHS employs a vehicle capsule within a protected vacuum tube deck, supported by reinforced concrete piers (i.e. multi-span viaduct). The tube environment allows multiple UHS vehicles to run in parallel simultaneously (i.e. twin tube deck) where asymmetric train loading will result in a large dynamic unbalanced moment on the piers. Therefore, exploring the lateral dynamic interaction of bridge deck (twin tube) and piers under such an unbalanced moment is an extremely important factor for analysis of viaducts under dynamic UHS train loading. Hence, this paper analytically addresses the dynamic bridge deck-pier interaction under UHS train loading for lateral vibration
Experimental evaluation of structural model and ground motion characteristics effects on RC bridge piers
No full textThis study reports a set of benchmark shaking table tests of four large-scale RC columns. Three of columns have identical design dimensions and details. They are subjected to three difference ground motions: (i) a near-field without pulse record, (ii) a near-field pulse-like record and (iii) a far-field record. All three records are spectrally matched to a common elastic spectrum. These particular benchmark column tests are designed to explore the influence of non-ergodic properties of the ground motion time-series on the seismic performance of RC bridge piers. The fourth column is identical in geometry and main-reinforcement detailing, however, it is lightly confined with larger horizontal ties spacing. The same far-field ground motion is used to test this column to examine the confinement effects on RC bridge piers during an earthquake
Exploring Bridge Dynamics for Ultra-high-speed, Hyperloop, Trains
Full text linkIn this paper the dynamics of a set of ultra-high-speed (UHS) moving masses/loads traversing a continuous beam are explored. The proposed model is intended to simulate the dynamic response of continues bridges under the new Hyperloop/Transpod trains, which are proposed to travel at up to 1200 km/h. This speed introduces a range of dynamic responses that have hitherto not been observed in generic high-speed trains. The analytical results show that the dynamic amplification factors, due to train passage, are significantly larger than current trains. This is due to the combination of ultra-high-speed and continuous beam construction, which is necessary to maintain a partial vacuum in the enclosed tube. Therefore, current design recommendations are not sufficient for these UHS trains.</p
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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