104,924 research outputs found
A survey of the turbulence statistics of a model-scale installed jet at low and moderate mach numbers
No full textIn modern high-bypass ratio engine configurations, the exhausted jet is deflected and modified by the wing and high lift devices. The present paper reports a survey on a model-scale jet in the presence of a flat plate installed at two height (h) and two length (l) positions from the center of the nozzle. The aim of this work is to evaluate the one-point statistics of isolated and installed jets. Experimental data of the axial component of the velocity is acquired for a 1½” nozzle via hot-wire anemometry. The investigation is made for several jet velocities, ranging from acoustical Mach numbers 0.2 to 0.8. Mean velocity profile results show a slight acceleration of the jet in regions close to the plate. This effect is notorious for plate locations in which the jet wets the plate close to the nozzle exit. It also seems to have a weak velocity dependency. This acceleration of the jet is consistent with the conservation of mass and changes in the entrainment at that region. As a direct result of the local jet acceleration, locations close to the plate present lower levels of turbulence intensity. Other factor that may contribute to this effect is the break-down of the eddies at the rigid surface. Turbulence intensity profiles have also shown a spike immediately downstream of the trailing edge. This is possibly an effect of the boundary layer separation, or a wake-type of flow originated at the trailing edge. Results for low and higher-order statistics of the shear layer opposite to the plate are exactly the same as results measured for the isolated jet configuration. Boundary layer development along the plate in both streamwise and spanwise direction is presented. It is shown that, even though the present problem consists of a non-uniform flow interacting with a surface, boundary layer properties could be defined for close-coupled, long surfaces. Finally, the spectra information from hot-wire sensors are analysed and qualitatively compared to the spectra measured by near-field surface pressure transducers located streamwise along the plate. The power spectral density of the velocity signal has a -5/3 decay, which is not seen in the pressure spectra.</p
Guest Editorial Introduction to the Special Issue on “Biometrics Based Methods for Healthcare Applications”
No full textEditorial to special issue on novel insights on ocular biometrics
No full textThis Editorial introduces the papers published in the Special Issue on "Novel Insights on Ocular Biometrics" o the Elsevier Journal Image and Vision Computing
Visual and textual explainability for a biometric verification system based on piecewise facial attribute analysis
No full textThe decisions behind the mechanics of a biometric verification system based on Machine Learning (ML) are difficult to comprehend. Although there is now well-established research in various fields of application, such as health or justice, the use of ML-based methods is accompanied by a lack of confidence that results in their limited use. The explainability of a ML system and the comprehension of what lies behind its prediction is one of the numerous characteristics that define "trust" in these systems. Over the years, face-based biometric authen-tication has been the subject of extensive research in both academia and industry. However, existing biometric authentication systems still have problems regarding accuracy, robustness and, explainability. Still lacking in the literature is a comprehensive examination of the use of post-hoc explainability techniques for such systems. Cognitive neuroscience has always been interested in the method by which people perceive faces; local elements such as the nose, eyes, and mouth are critical to the perception and recognition of a face. In this work, starting from this assumption, we propose a framework of visual and textual explainability based on the parts of a face by analyzing them with respect to the facial attributes reported in the CelebA dataset. The primary objective is to be able to explain why two pictures of different subjects are distinct. This is done by sinthesizing pairs of images that illustrate how dissimilar the various parts of the face under investigation are and incisive and direct textual explanations of the distinguishing features are generated. A further study analyzes an interpretable mapping between the semantic space of the text and the space of the image. (c) 2023 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
On the Performance of the H-H Test
No full textHorowitz and HardIe (1992) proposed a procedure for testing a parametric model against a semiparametric alternative (called the H-H test) which is based on the evaluation of moment conditions following the methodology presented by Newey (1985). Their approach is related to Bierens (1990) test to detect any kind of model misspecification also based on Newey's framework. It is shown that these tests procedures are consistent (the asymptotic power is equal to 1 in the set of alternatives). However the absence of information about their finite sample properties make simulations required to evaluate their quality on discriminating model misspecification. In this paper the small sample performance of the H-H test is analized concerning the empirical power and size by a Monte Carlo study with single index models. The results are compared with those obtained using Bierens' test.
25th ICPR-Real-time Visual Surveillance as-a-Service (VSaaS) for smart security solutions
No full textAppropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
No full textWe 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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
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