1,720,970 research outputs found
Complex modes identification via Hilbert transform
No full textAmong the numerous identification methods available for operational modal analysis, the CPR (Complex Plane Representation) method proves efficient and effective in the case of sweep tests where the excitation is not measured. The CPR method has been described in a number of papers by the authors and allows for high precise identification of the modal parameters. In spite of this precision there exist cases where the approximations involved by practical applications need further clarification. The paper is devoted to estimate error bounds due to lack of congruence between the theoretical assumptions and the actual system characteristics or field conditions. The dependence of the amplitude and phase values on the modal density is crucial in this respect. Theoretical and numerical solution are used to validate the CPR results
The Complex Plane Representation Method for Structural Damage Detection
No full textModal parameters are often used for damage identification purposes in the dynamic field. Commonly, shifts in the modal parameters between different states are assumed as measures of damage. Frequency shifts are easily detected, but in some circumstances they are not sensible to damage. In spite of its imprecise identification, damping possesses generally a monotonic variation with damage. Modal shapes exhibit increasing complexity along with damping increase. Operational modal shapes are identified using the CPR method and used to construct indicators capable to detect damage. The effectiveness of the method and the indicators is shown against theoretical data and numerical simulation
Evaluation of building seismic retrofitting costs foundedon experimental data. The case study of "San Benedetto" School (Norcia, Italy)
No full textEvaluation of seismic retrofitting costs, a key issue in the risk mitigation strategies, requires the estimation of the building performance and the forecast of the site response. In addition, a target building performance should be a priori defined. In this study, a procedure to provide seismic retrofitting costs is suggested with reference to a case study, based on what following: i) the building performance is described by fragility curves obtain via recorded data on the building itself (Seismic Model from Ambient Vibration - SMAV), ii) the local seismic site response is estimated by means of numerical one-dimensional simulation based on site-specific data or by means of simplified technical code approach, iii) the building performance and the site response are combined in order to obtained an Annual Frequency of Failure for each damage limit state, iv) this frequency is compared to the target allowable reliability level according to the classes of use and limit states of building in order to obtained a Vulnerability index, v) seismic retrofitting costs, depending on the Vulnerability index values, are evaluated from literature suggestions (Cat erino et alii, 2018). Finally, with reference to the case study of the "San Benedetto" school of Norcia (Central Italy), the proposed methodology is satisfactorily verified by comparing the forecast with real costs. The innovative aspect of the proposed methodology lies in the use of the recorded data and SMAV model and in the procedure for defining the local seismic response which considers the building-specific characteristics and the site-specific conditions
Effects of modal density in system identification using the Hilbert transform
No full textThe paper aims to review and deepen the effects of the modal density in the dynamical identification with the Complex Plane Representation (CPR) method that is based on the Hilbert transform of the motion response of mechanical systems. It is demonstrated that the strong accuracy in the identification of the modal parameters with the CPR method can be somewhat corrupted for high modal densities. Theoretical and numerical solutions are used to analyze the problem and validate the CPR results
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
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