1,720,977 research outputs found
The Systematic Study of African Dress and Textiles.
No full textSmith, F.T.; Eicher, J.B.. (1982). The Systematic Study of African Dress and Textiles.. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/162479
AVM modelling by multi-branching tube flow: large flow rates and dual solutions
No full textCerebral arteriovenous malformations (AVMs) present a common yet complex clinical challenge, through ÔstealÕ phenomena, haemorrhage risks and epilepsy effects, aspects which are little understood even for individual lesions. The main difficulty lies in understanding the detailed haemodynamics of AVMs and especially the enhanced through-flow associated with steal. Mathematically, as a basic step, the paper investigates a nonlinear inviscid model for the planar incompressible flow of fluid through a branched geometry consisting of a single feeding mother tube which splits into two or more non- aligned daughter tubes. Recurrence relations between the unknown flow profiles in the daughter tubes and the incoming rotational flow profile in the mother tube are derived, analysed, and solved in detail in order to find the total flow rate. The results show greatly enhanced through-flow arising, for a fixed value of the total downstream flow area, either from non-unique solutions to the problem or more particularly from an increase in the number of daughter tubes, or from both, depending on the distribution of pressure differences applied across the branching region and the total downstream flow area. Extensions of the basic flow model are noted, along with comparisons with recent direct numerical simulations and discussion of possible repercussions in the context of treatment and clinical observations of enhanced through-flows in AVMs
Fluid motion for car undertrays in ground effect.
No full textAir motion representative of some of the flows past a moving car is studied, particularly in the gap between the car underbody (undertray, front flap or forewing) and the ground, using theory and computation. The ground-affected flows encountered are two- or three-dimensional, laminar, transitional or turbulent, and attached or separated. Given Reynolds numbers in the approximate range 1–10 million, emphasis here is placed first on key physical flow mechanisms: viscous-inviscid interaction filling either much or part of the gap; the generation of strong upstream influence; an abrupt pressure jump at the leading edge; the moving-ground condition; substantial diffuser flow reversals and wake effects; in three dimensions the distinguishing between inflow and outflow edges; and turbulent flow modelling. Second, for various underbody shapes, predictions are presented of the surface pressures and shear stresses, the lift or downforce, and the velocity profiles. Extensions of these to include edge effects, three-dimensionality and turbulence modelling are examined, along with optimization for certain shapes concerned with front-flap design and comparisons with recent experiments
One-to-few and one-to-many branching tube flows.
Full text linkBranching tube flows are examined, for one mother to two, three or more daughter tubes. The case of many daughters (abrupt multi-branching) models blood flow through an arteriovenous malformation in the brain, while that of very few daughters (gradual branching) applies elsewhere in physiology and surgical grafting, as well as other applications including industrial ones. Theory and computation are presented for two- and three-dimensional motions, under the viscous and inviscid effects of small changes in mass flux between the daughter tubes, area expansion and turning of the flow. Specific configurations for which flow solutions are obtained are (a) with two large daughters, (b) with one small daughter/side branch, and (c) with multiple small daughters.The numerous physical mechanisms acting concern overall upstream influence and through-flow, and flow separation and criteria for its avoidance, as well as criteria for the amount of turning and area expansion possible without energy loss and other factors associated with separation, and the role of the branching geometry versus that of the mass-flux distribution in the daughters. In particular, configuration (a) allows substantial separation-free turning and expansion only with certain shaping of the outer wall and an area expansion ratio typically less than 1.2, whereas more daughters involve a balance between geometry and mass flux. In (b), an abrupt pressure jump is induced at the mouth of the small daughter, near which mass-flux effects tend to dominate over geometrical shaping effects. In (c), as the number of daughters increases, the amount of separation-free turning and expansion is found to increase substantially, and the distributed mass-flux influence readily overrides the geometrical influence throughout the branching; there is also an integrated upstream effect of the multi-branching on the incident mother flow even though each daughter flow acts as if independent. Tentative designs based on wall shaping, flux distributions and divider placement are considered for flow improvement/surgery
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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