1,721,197 research outputs found
Local Scour by Turbulent Jets
No full textThe present study investigates with laboratory experiments the scour downstream of a sill, followed by a rigid apron, in clear water scour conditions. Nine experiments were run, changing the discharge and the tailwater depth of the flow. The temporal evolution of the scour was recorded by a video camera and measured using image analysis techniques. The velocity field was measured by an ultrasonic velocity profiler, both over the rigid apron and in the scour hole. The dimensionless scour profiles showed geometrical similarity for all the runs, if the maximum scour depth, Dsmax was used as length scale of the vertical and horizontal distances, respectively. The mean velocity profiles, measured over the rigid apron, were similar to a wall jet modified by the existence of a reverse flow close to the water surface. The mean velocity profiles, measured along the scour hole, were similar to an asymmetrical free jet, using as scales the maximum mean velocity, Um, and the distances from the plane of Um to the planes where the velocity was Um/2
Thermal and microstructural analysis of the Y-Ba-Cu-O/Ag equilibrium around the critical composition YBa2Cu3Ox/Ag35 mass%
No full textContribution to the study of phase interactions and morphology in YBCO/Ag melt-processed composites
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Influenza degli errori di misura del L.D.A. nella valutazione dei gradi di libertà di sistemi dinamici
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The influence of measurement errors on the determination of the degrees of freedom of dynamical systems
No full textWe consider the influence of measurement errors on the experimental calculation of dimensions of possible turbulent flow attractors. For this purpose we considered a Gaussian noise and we carried out some tests showing the existence of a lower limit below which the operational definition of dimension is not reliable
A mathematical model for a diluted two-phase flow
No full textThe aim of this work is to model the forces exchanged by the liquid and aeriform phase in a two-phase flow. Assuming that the aeriform is constituted by spherical bubbles, far enough each other in order to exclude reciprocal interactions, introducing a suitable phase average operation and describing the motion of the bubbles, relative to the liquid phase, the forces exchanged by the two phases can be finalyy expressed as functions depending on the macroscopic parameters of the motion. Accounting for such forces in motion equations, a partial differential system describing the evolution of the two-phase flow is obtained. The mathematical model is then applied in order to simulate water hammer experimental results. The comparison between numerical and experimental results is good, indicating that the modeling of the inter phase momentum exchange term has been correctly performed
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
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