1,720,968 research outputs found
Assessment of the derating methods for centrifugal pump performance handling non-Newtonian fluids
No full textOil and Gas applications commonly require the displacement of a huge amount of processing fluids. In most cases, these fluids consist of solid rock particles transported by water, e.g. kaolin or bentonite powder, which show non-Newtonian behavior. For this kind of fluid positive displacement pumps are usually recommended, but where high flow rates have to be guaranteed, centrifugal pumps are installed. Since most of the manufacturers provided the performance curves only with water, choosing the appropriate centrifugal pump to handle mineral slurries may be very challenging. Since the viscosity of this kind of fluids varies with the imposed stress and rheology, pumping this type of fluids can lead to a considerable variation in the pump head, and thus, overall efficiency is difficult to-be-predicted. Several reliable methods to predict the centrifugal pump performance in handling high-viscous Newtonian fluids can be found in literature, e.g. the well-known Hydraulic Institute method. Nevertheless, no general practical correlations are provided for non-Newtonian fluids. Previous experimental investigations on centrifugal pumps reported high-performance instabilities at low flow rates when non-Newtonian fluids are considered. Further investigations are needed to define which parameters in the pump fluid interaction have to be considered in the derating process. In this work, an assessment of the prediction quality of the existing derating methods from the literature is carried out. For this purpose, the data obtained from previous experimental investigations on a small commercial centrifugal pump handling mixtures of water and kaolin are considered
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
Experimental analysis of the micro-sized particle adhesion in a subsonic stationary cascade
No full textThe particle deposition phenomenon represents the critical factor for studying gas turbine fouling. Solid particle adhesion drives the contamination of the relevant surfaces of the power unit. Both compressor and turbine sides are affected by the performance degradation over time due to the contaminant adhesion. The performance losses are strongly related to the contaminants’ characteristics and the gas turbine’s operation. Solid contaminants like soil or soot coupled with environmental conditions such as temperature and humidity modify their stickiness, determining a difficult to predict effects on the gas turbine operation and reliability. According to the blade shape, surface characteristics, and flow field structures, particle impact determines the deposited layer growth process or the detachment/spallation of the previously deposited layer. This work analyzes the sticking and detachment processes generated by the interaction between solid substrate and micro-sized solid particles. The tests are carried out on a stationary linear subsonic cascade in which soil and soot particles are used to contaminate the flow field. A sensitivity analysis of the relative humidity values has shown how a slight increase in the relative humidity values determines the increment of the deposited contaminants by an order of magnitude. Blade regions and the overtime assessment of sticking and detachment processes are also assessed. Microsized contaminants interact with the blade surface, modifying the shape of the leading edge and the surface roughness, especially on the pressure side
A LOW-NOISE AIRFOIL FOR LOW REYNOLDS APPLICATIONS: A MULTI-FIDELITY OPTIMIZATION
No full textAutomotive fans, small wind turbines, and manned and unmanned aerial vehicles (MAVs/UAVs) are just a few of the examples in which noise generated by the flow interaction with the aerodynamic surfaces is a major concern. The current work shows the potential of a new airfoil shape to minimize noise generation, maintaining high lift-to-drag ratio in the low-Re regime (Re ≤2e5). The investigation is carried out by means of a multi-fidelity approach: a low-fidelity semi-empirical model is exploited for evaluating the sound pressure level (SPL). The fast evaluation of the low-cost function enables the computation of a large range of possible profiles, and accuracy is added to the low-fidelity response surface with high-fidelity CFD data. The constraint of maintaining a pre-defined range of the lift coefficient and lift-to-drag ratio ensures the possibility of using this profile in usual design procedures
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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