1,720,957 research outputs found
Accurate evaluation of edges and dip of faults and contacts through the Volume Upward Continuation (VUC) of gravity data
No full textIn this paper we demonstrate the efficiency of a new approach to upward continue potential field data, the Volume Upward Continuation (VUC), coupled with traditional horizontal derivative techniques. By using VUC it is immediate showing that upward continuation of the signal to higher altitudes yield information about progressively deeper sectors of the discontinuity. In particular, looking at the position of the maxima of the horizontal derivative of the continued field, we can observe that they will be laterally shifted toward the dipping direction of the discontinuity, in a way proportional to the continuation height.
We applied VUC followed by horizontal derivative to a gravity profile extracted from a gravity survey on the Venelin-Aksakov fault in Bulgaria, in order to get further information on the dipping direction of this structure
Volume Continuation of potential fields from the minimum-length solution: An optimal tool for continuation through general surfaces
No full textMany methods have been used to upward continue potential field data.Most techniques employ the Fast Fourier
transform, which is an accurate, quick way to compute level-to-level upward continuation or spatially varying
scale filters for level-to-draped surfaces. We here propose a new continuation approach based on the
minimum-length solution of the inverse potential field problem, which we call Volume Continuation (VOCO).
For real data the VOCO is obtained as the regularized solution to the Tikhonov problem. We tested our method
on several synthetic examples involving all types of upward continuation and downward continuation (levelto-
level, level-to-draped, draped-to-level, draped-to-draped). We also employed the technique to upward
continue to a constant height (2500 m a.s.l.), the high-resolution draped aeromagnetic data of the Ischia Island
in Southern Italy. We found that, on the average, they are consistent with the aeromagnetic regional data
measured at the same altitude. The main feature of our method is that it does not only provide continued data
over a specified surface, but it yields a volume of upward continuation. For example, the continued data refers
to a volume and thus, any surface may be easily picked up within the volume to get upward continuation to
different surfaces. This approach, based on inversion of the measured data, tends to be especially advantageous
over the classical techniques when dealing with draped-to-level upward continuation. It is also useful to obtain
a more stable downward continuation and to continue noisy data. The inversion procedure involved in the method
implies moderate computational costs, which are well compensated by getting a 3D set of upward continued
data to achieve high quality results
Volume upward continuation of potential fields from the minimum-length solution: an application in environmental hazards mapping
No full textWe propose a new approach, based on the
minimum-length solution of the inverse potential field problem.
The method yields a volume upward continuation, and reveals to
be advantageous over the classical techniques when dealing with
truncated anomalies and when draped-to-level upward
continuation is needed. One of the advantages of the novel
approach is that the VUC (Volume Upward Continuation) method
yields a volume upward continuation, and thus it may be used to
extract in a simple way the continuation on any kind of surface
and also to multiple levels
Volume upward continuation of potential fields from the minimum-length solution: an optimal tool for continuation through general surfaces
No full text
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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