Three dimensionality in the wake of the flow around a circular cylinder at Reynolds number 5000

The turbulent flow around a circular cylinder has been investigated at Re=5000Re=5000 using direct numerical simulations. Low frequency behavior, vortex undulation, vortex splitting, vortex dislocations and three dimensional flow within the wake were found to happen at this flow regime. In order to successfully capture the wake three dimensionality, different span-wise lengths were considered. It was found that a length LZ=2pDLZ=2pD was enough to capture this behavior, correctly predicting different aspects of the flow such as drag coefficient, Strouhal number and pressure and velocity distributions when compared to experimental values. Two instability mechanisms were found to coexist in the present case study: a global type instability originating in the shear layer, which shows a characteristic frequency, and a convective type instability that seems to be constantly present in the near wake. Characteristics of both types of instabilities are identified and discussed in detail. As suggested by Norberg, a resonance-type effect takes place in the vortex formation region, as the coexistence of both instability mechanisms result in distorted vortex tubes. However, vortex coherence is never lost within the wake.Peer ReviewedPostprint (author's final draft

Feed preference in pigs: Relationship between cereal preference and nutrient composition and digestibility

The present work aimed to identify the nutritional characteristics that best explain cereal feed preference in pigs. A total of 25 cereals of known preference (at 60% of inclusion in complete feed) from a previous study were evaluated. The cereals were analyzed for DM, OM, crude fiber, ether extract, CP, GE, digestible starch, and glycemic index. Additionally, for 12 of the cereals, complete feeds (the same composition as those previously used to measure preference) were prepared, analyzed for DM, OM, CP, and starch, and fed to pigs (33 ± 5.1 kg BW) fitted with ileal T-cannulae to assess the apparent ileal (AID) and total tract digestibility (ATTD) of these nutrients using titanium dioxide as an indigestible marker. The relationships among the different energy and nutrient contents were studied by principal component (PC) analysis, and the correlations between the generated PC scores and cereal preference were analyzed. A correlation between preference and the second PC obtained with data of the 25 cereals was observed (P < 0.01), which indicated that crude fiber (negatively) and digestible starch, OM, and glycemic index (positively) were correlated with feed preference. Statistically significant linear relationships with preference were confirmed for crude fiber, digestible starch, and glycemic index (R = 0.38, 0.36, and 0.23, respectively; P < 0.02). Similarly, the first PC obtained with data of the 12 feeds also correlated with preference (P < 0.01), indicating that the digestible nutrients (positively) and the nondigestible nutrients (negatively) were correlated with preference. Statistically significant relationships with preference were observed for the contents of starch (total, digestible AID, and digestible ATTD: R = 0.62, 0.66, and 0.63, respectively; P < 0.01), AID DM (digestible and nondigestible: R = 0.41 and 0.44, respectively; P < 0.05), ATTD DM (digestible and nondigestible: R = 0.67 and 0.70, respectively; P < 0.01), AID OM (digestible and nondigestible: R = 0.45 and 0.43, respectively; P < 0.05), and ATTD OM (digestible and nondigestible: R = 0.64 and 0.66, respectively;

Tunneling conductance in Superconductor/Ferromagnet junctions: a self consistent approach

We evaluate the tunneling conductance of clean Ferromomagnet/Superconductor junctions via a fully self-consistent numerical solution of the microscopic Bogoliubov-DeGennes equations. We present results for a relevant range of values of the Fermi wavevector mismatch (FWM), the spin polarization, and the interfacial scattering strength. For nonzero spin polarization, the conductance curves vary nonmonotonically with FWM. The FWM dependence of the self-consistent results is stronger than that previously found in non-self-consistent calculations, since, in the self-consistent case, the effective scattering potential near the interface depends on the FWM. The dependence on interfacial scattering is monotonic. These results confirm that it is impossible to characterize both the the FWM and the interfacial scattering by a single effective parameter and that analysis of experimental data via the use of such one-parameter models is unreliable.Comment: 12 pages, including 8 figure

A blue sky catastrophe in double-diffusive convection

A global bifurcation of the blue sky catastrophe type has been found in a small Prandtl number binary mixture contained in a laterally heated cavity. The system has been studied numerically applying the tools of bifurcation theory. The catastrophe corresponds to the destruction of an orbit which, for a large range of Rayleigh numbers, is the only stable solution. This orbit is born in a global saddle-loop bifurcation and becomes chaotic in a period doubling cascade just before its disappearance at the blue sky catastrophe.Comment: 4 pages, 6 figures, REVTeX, To be published in Physical Review Letter

Predicting Audio Advertisement Quality

Online audio advertising is a particular form of advertising used abundantly in online music streaming services. In these platforms, which tend to host tens of thousands of unique audio advertisements (ads), providing high quality ads ensures a better user experience and results in longer user engagement. Therefore, the automatic assessment of these ads is an important step toward audio ads ranking and better audio ads creation. In this paper we propose one way to measure the quality of the audio ads using a proxy metric called Long Click Rate (LCR), which is defined by the amount of time a user engages with the follow-up display ad (that is shown while the audio ad is playing) divided by the impressions. We later focus on predicting the audio ad quality using only acoustic features such as harmony, rhythm, and timbre of the audio, extracted from the raw waveform. We discuss how the characteristics of the sound can be connected to concepts such as the clarity of the audio ad message, its trustworthiness, etc. Finally, we propose a new deep learning model for audio ad quality prediction, which outperforms the other discussed models trained on hand-crafted features. To the best of our knowledge, this is the first large-scale audio ad quality prediction study.Comment: WSDM '18 Proceedings of the Eleventh ACM International Conference on Web Search and Data Mining, 9 page