1,721,099 research outputs found
Multiscale estimation of excess mass from gravity data.
No full textWe describe a multiscale method to estimate the excess mass of gravity anomaly sources,
based on the theory of source moments. Using a multipole expansion of the potential field and
considering only the data along the vertical direction, a system of linear equations is obtained.
The choice of inverting data along a vertical profile can help us to reduce the interference effects
due to nearby anomalies and will allow a local estimate of the source parameters. A criterion
is established allowing the selection of the optimal highest altitude of the vertical profile data
and truncation order of the series expansion. The inversion provides an estimate of the total
anomalous mass and of the depth to the centre of mass. The method has several advantages
with respect to classical methods, such as the Gauss’ method: (i) we need just a 1-D inversion
to obtain our estimates, being the inverted data sampled along a single vertical profile; (ii) the
resolution may be straightforward enhanced by using vertical derivatives; (iii) the centre of
mass is also estimated, besides the excess mass; (iv) the method is very robust versus noise;
(v) the profile may be chosen in such a way to minimize the effects from interfering anomalies
or from side effects due to the a limited area extension. The multiscale estimation of excess
mass method can be successfully used in various fields of application. Here, we analyse the
gravity anomaly generated by a sulphide body in the Skelleftea ore district, North Sweden,
obtaining source mass and volume estimates in agreement with the known information. We
show also that these estimates are substantially improved with respect to those obtained with
the classical approach
Development of a Numerical Methodology Able to Simulate the Unstable Mixed Mode Delamination Growth in Stiffened Composite Panels Under Cyclic Loading Conditions
No full textAeronautical structures, often, experience impacts with foreign objects in service and during maintenance operations. Foreign Objects Impacts (FOI) can lead to critical damages and can compromise the overall performances of structural components. Indeed, among the others, composite components can exhibit various interacting post impacts damage mechanisms, including fiber breakage, matrix fracture, and interlaminar damages, such as delamination between different layers of the laminates. Delamination represents the most critical failure mechanisms, as it is, often, undetectable by visual inspections and it may, unstably and silently, develop within the component. This Phenomenon may be amplified under cyclic loading conditions, as the residual strength and stiffness can decrease rapidly after a certain number of cycles, potentially leading to structural collapse [1]. Unstable propagation of delaminations is particularly critical, since it, actually, can take place without the need of increasing the load acting on the structure. This phenomenon, which is very dangerous for the structural integrity of components, can be very challenging to be predicted, under fatigue loading conditions, by the standard geometrically non-linear Finite Elements Methodologies (FEM) which use a sequence of simulations under force control to mimic the fatigue behaviour of composite materials. Actually, FEM simulations under controlled force levels lead to convergence issues when predicting the highly dynamic behaviour of the unstable growth of delaminations under fatigue loading conditions. The research activity, presented in this paper, is aimed to develop an alternative efficient methodology able to mimic the unstable delamination propagation under cyclic loading conditions in composite structures by non-linear static analyses. This new methodology has been demonstrated to be able to correctly consider the fast variation of delamination size associated to decrease in loading during the unstable growth phenomenon under cyclic loading conditions. To achieve this objective, the Paris Law [2, 3] approach has been implemented in the ANSYS FEM code together with an enhanced Virtual Crack Closure Technique (VCCT) based method
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
- …
