1,721,167 research outputs found
Experimental study of the forming process: Fluid velocity and fluid-fiber interaction measurements
No full textA study of the flow in the direct vicinity of a forming wire and a fiber network during forming is reported. The measurements are performed with Particle Image Velocimetry in a scaled system. Index-of-refraction matching is used to gain optical access to the flow. Time resolved measurements of the flow velocity in the vertical and horizontal direction is obtained in a plane with a size of 60 × 40 fiber diameters. The spatial resolution is 2 fiber diameters. Data is obtained for three drainage velocities and two different lengths of the fibers. The relative level of the velocity fluctuations are found to decrease with drainage velocity and is higher in the flow above a network mat of shorter fibers compared to the network made of longer fibers. The size of the flow structures is obtained by spectral analysis and compared for the six cases
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
Performance Analysis of Two-Dimensional Plane Diffusers at a Moderate Reynolds Number by Means of Unsteady RANS
No full textDiffusers are devices found in several engineering applications and their performance and design are object of numerous investigations. However, relatively few investigations have been dedicated to diffusers operating at low and moderate Reynolds numbers. In this regime, the flow could be laminar, turbulent or transitional, and the aerodynamic performance of the diffuser becomes highly dependent on the specific value of the Reynolds number and inlet conditions. In particular, the present study focuses on evaluating the role of inlet conditions on the performance and flow behaviour of two-dimensional diffusers on this specific Reynolds number regime (Re≈8000). Furthermore, the diffuser discharges in a stationary chamber and it does not present a tail-pipe configuration, a condition that has not found a clear presence in the existing literature so far. A numerical investigation of two-dimensional plane diffusers was performed at Re=8163 for 9 different cases, combined varying the inlet turbulence intensity (0.05, 3, and 10 percent), and the velocity profile, characterised by different blockage factors (0, 0.05 and 0.33). For each case, the divergence angle ranged from 0 to 30 degrees, and several URANS simulations were performed using the k-ωTransitional SST model that accounts for the possible transition of the boundary layer. The results show that the design recommendations valid for high Reynolds number diffusers with a thin boundary layer are not always applicable, and extreme caution must be exercised when dealing with operating conditions that do not ensure a sufficiently high turbulence level at the inlet. The divergence angles of the stall regimes are shown, and performance indicators (e.g. pressure-recovery coefficients) are reported. These reveal a strong decrement (up to 60 percent) of the pressure recovery on reducing turbulence intensity from 10 percent to 0.05 percent. The blockage factor of the velocity profile has an important effect on performance as well. In order to simplify the comparison between the different blockage factors, a modified effectiveness was employed to account for the distortion introduced by a non-uniform inlet velocity profile
FRC measurement by a modified helium dilution technique in ALI/ARDS patients: Comparison with helical CT-scan
No full textUncertainty analysis of the Von Kàrmàn constant for the mean centerline velocity in CICLoPE
No full textPerformance analysis and optimal sizing of electric multirotors
Full text linkThis paper presents an analytical framework for addressing the hovering performance of a battery–powered multirotor. The estimation of power required for flight is investigated and an analytical model is proposed to describe the rotor figure of merit as a function of few relevant blade parameters, without the need for ad hoc experiments. The model is derived after a discussion about the aerodynamics of rotating blades. The formulation in terms of Reynolds number is supported by an experimental campaign, performed on a set of commercial–of–the–shelf propellers optimized for small–scale multirotor applications. By imposing the balance between required and available power, the hovering time is predicted by an integral formulation developed for a constant–power battery discharge process. The best endurance condition is obtained in terms of optimum battery capacity and flight time. The methodology, applicable to the design phase of novel multirotor configurations, is finally validated by flight tests
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
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