1,720,961 research outputs found
PIV measurements of sloshing flow in a rectangular tank induced by a sinusoidal inflow
No full textAn experimental study of the flow field in a rectangular tank filled with water and forced by a speaker has been carried out by using particle image velocimetry (PIV) technique. The employed experimental apparatus is sketched in figure 1. The speaker oscillation creates a disturbed field which determines a periodically waving of the free surface on the upper part of the tank. Phase-locked measurements have been performed sampling the investigated phenomenon each 12° obtaining 30 phases. Several depths d (8cm, 6cm and 4cm), working frequencies f (1.825 Hz, 2.8 Hz, 3.4 Hz) and wave amplitudes have been tested. In particular, for a fixed depth and working frequency, the wave amplitude equal or more than 10% compared to the maximum depth of the tank is obtained varying the supply voltage V. In figures are represented the PIV measurements in the following conditions: f = 2.8Hz, V = 800mV, d = 8cm of water. The phases φ=264° - φ=336° are characterized by the formation of a vortex structure such like a synthetic jet starting from the speaker outflow. This expulsion phase causes free surface oscillation with the formation of a non-sinusoidal free surface. The non-regular behavior of the free surface is caused by the contrast between the fluid going backward from the previous phases and the new injected fluid in forward direction. During the entire expulsion phase, the vortex structure is generated and convects downstream until it reaches a distance of about x=3.5w where the vortex dissolves. Simultaneously, the free surface has a sinusoidal trend as expected because of the periodical forcing. The vortex structure gets smaller while it proceeds along the tank floor because of two main reasons: diffusion of kinetic energy and interaction with the descending free surface. This interaction stops the downstream evolution of the vortex structure which collapses under the water mass moving downward. After the vortex has dissolved, the suction phase starts and causes the downward movement of the free surface at x 8w
Dynamic Thermal Behavior of a GDI Spray Impacting on a Heated Thin Foil by Phase-Averaged Infrared Thermography
No full textINVESTMENT CASTING PROCESS: 3D TEMPERATURE MAP RECONSTRUCTION OF A CERAMIC SHELL MOLD
No full textThe purpose of this work is to experimentally reconstruct the 3D temperature map of a ceramic shell mold and to investigate its time-dependent thermal behavior during the final part of the investment casting process. The investment casting process is the most used technique to produce very reliable components. Nowadays, there are still too much failing processes that are unacceptable in terms of both plant downtime and material waste. These failing processes are mainly caused by a non-uniform cooling that can promote thermal gradients in the components leading to a generation of residual thermal stresses.
The experimental 3D temperature map reconstruction and its time-dependent behavior are analyzed through the Infrared Thermography technique. Such a reconstruction allows to observe the presence of strong temperature gradients and quantify them. In the present case, the central part of the investigated ceramic shell mold shows strong temperature gradient. This central part is of extreme importance because of the presence of the blades housings. The temperature difference present on the blades housings increases with time leading to stronger temperature gradient
INVESTMENT CASTING PROCESS: 3D TEMPERATURE MAP RECONSTRUCTION OF A CERAMIC SHELL MOLD
No full textThe purpose of this work is to experimentally reconstruct the 3D temperature map of a ceramic shell mold and to investigate its time-dependent thermal behavior during the final part of the investment casting process. The investment casting process is the most used technique to produce very reliable components. Nowadays, there are still too much failing processes that are unacceptable in terms of both plant downtime and material waste. These failing processes are mainly caused by a non-uniform cooling that can promote thermal gradients in the components leading to a generation of residual thermal stresses.
The experimental 3D temperature map reconstruction and its time-dependent behavior are analyzed through the Infrared Thermography technique. Such a reconstruction allows to observe the presence of strong temperature gradients and quantify them. In the present case, the central part of the investigated ceramic shell mold shows strong temperature gradient. This central part is of extreme importance because of the presence of the blades housings. The temperature difference present on the blades housings increases with time leading to stronger temperature gradient
Towards enabling time-resolved measurements of turbulent convective heat transfer maps with IR thermography and a heated thin foil
Full text linkThe temperature of a heated foil, exposed to a turbulent flow, changes continuously in time due to the fluctuation of the convective heat transfer coefficient. Measuring with enough temporal resolution the foil temperature map and solving the unsteady energy balance of the foil can allow restoring the instantaneous value of the convective heat transfer coefficient. Nevertheless, the high characteristic frequencies of turbulent flows (especially in air) result in very small temperature fluctuations, which are typically hard to measure with an infrared camera. This work presents a novel filtering approach based on Proper Orthogonal Decomposition which allows to dramatically reduce the measurement random noise, thus enabling the detection of small temperature fluctuations and, as a consequence, to improve the estimate of instantaneous distributions of the convective heat transfer coefficient. The proposed methodology is tested on synthetic jets impinging on a foil, actuated with a loudspeaker at various actuation frequencies. The measurement capabilities of the present technique are assessed through comparison with measurements obtained from raw data and phase averaged measurements
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
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