1,720,961 research outputs found
Structural damage detection in composite aeronautical components through methods based on digital filtering and wavelet transforms
No full textSeveral recent investigations have shown how visual inspections of mode shapes do not ensure an accurate, or even rough, identification of structural defects. This paper aims at exploring the applicability of a numerical-experimental method based on digital shape processing techniques for the identification of localised structural changes. The problem is tackled within an aeronautical context where the damage detection procedure is specifically applied to multilayered plates having symmetrically stacked layers. The examined components are used in the aeronautical industry during the manufacturing process of aircrafts and being, such structural components, an essential part for the integrity of the structure, they undergo extremely accurate investigations before becoming a part of the whole system. An interesting point here investigated is the possibility of offering a less demanding NDT alternative to those existing (i.e. ultrasonic). Several defects are simultaneously introduced into multilayered plates; these defects are simulated through a finite element model basing the model on a template derived from an ultrasonic benchmark. In order to evaluate the influence of real measurements in the identification of localised defects, noise has been artificially introduced in the model to simulate a reduced signal-tonoise ratio in accordance with currently available laser measuring technology. The capability of the presented techniques of identifying localised defects is compared with the ultrasonic benchmark and relevant conclusions are extracted
Structural damage detection in composite aeronautical components through methods based on digital filtering and wavelet transforms
No full textShimming Analysis of Carbon-Fiber Composite Materials with Eddy Current Testing
No full textThis paper investigates the use of the Eddy Current Testing (ECT) for detecting gaps between carbon-fiber composite materials, caused by overlapping of assembly parts with geometrical variations. To this purpose, we use two overlapped carbon-fiber reinforced plastic (CFRP) tapes, while an increasing number of PVC sheets are placed between these tapes to vary the thickness of the gaps. Several experiments are carried out. For everyone, and for each considered gap, three ECT response parameters are extracted. The obtained data are used to train different machine learning-based classifiers to distinguish the gaps. Their validation, assessed through the 10-fold cross validation technique, proves the effectiveness of ECT as gaps detector for CFRP materials
POSSIBILITA' DIAGNOSTICA DELLA PH-METRIA COMBINATA GASTRICA ED ESOFAGEA DI 24 ORE NELLO STUDIO DEL REFLUSSO DUODENO-GASTRICO (RDG) E DEL REFLUSSO GASTRO-ESOFAGEO (RGE) "NON ACIDO".
No full textAutomatic ultrasonic inspection for internal defect detection in composite materials
No full textThe detection of internal defects in composite materials with non-destructive techniques is an important requirement both for quality checks during the production phase and in-service inspection during maintenance operations. Visual inspection allows only the analysis of surface characteristics of materials and, then, if internal faults occur inside composite structures, a deeper analysis is required. A comparison between the reactions of different materials to ultrasonic signals can be used to highlight the difference in the internal structures and also to detect the depth position of these anomalies. However, ultrasonic data are difficult to interpret since they require the analysis of a continuous signal for each point of the material under consideration. An automatic procedure is necessary to manage large data sets and to extract significant differences between them. In this paper, we address the problem of automatic inspection of composite materials using an ultrasonic technique. We consider two main steps for interpreting ultrasonic data: the pre-processing technique necessary to normalize the signals of composite structures with different thicknesses and the classification techniques used to compare the ultrasonic signals and detect classes of similar points
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
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