Sound produced by a backward facing step under a wall jet

International audienceSound radiation by a backward facing step under a plane wall jet is examined. The investigation is based on an experiment where the mean velocity, the step heights and the cross-stream extent of the jet are varied. The comparison between the backward facing step flow and the corresponding wall jet shows the existence and some characteristics of a source located at the step. Computations of the sound radiated by the turbulent eddies and existing literature about sound sources near geometric singularities, indicate that the step is involved in the radiation of this source. It is shown that the step diffracts the sound of nearby passing eddies and that the sound level is significantly increased into the upstream directions. Flapping of the separated shear layer does not radiate soun

Study of the influence of microstructure on electric properties of plasma-sprayed aluminia coatings using the scanning electron microscope mirror effect (SEMME) method

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Influence of defect orientation on electrical insulating properties of plasma-sprayed alumina coatings

International audienceThe influence of the microstructure (pores and cracks) on electric properties of plasma-sprayed alumina coatings was investigated using the so-called Scanning Electron Microscope Mirror Effect (SEMME) technique. Coatings were sprayed with different alumina feedstock powders on various atmospheres using a CAPS (‘Controlled Atmosphere Plasma Spraying'). Microstructures with various amount of porosity and cracks orientation distributions were analysed. Both outer surfaces and cross-sections of alumina coatings have been analysed by SEMME technique using two complementary modes (measurement of absorbed current and mirror methods). Originally developed to study the behaviour of injected electrons and related phenomena, such as trapping ability, detrapping process and relaxation phenomena in bulk insulating materials, the SEMME technique was successfully applied, in this study, to porous coatings. It is proved that cracks orientation modifies both motion and trapping of charges and therefore the dielectric properties of plasma-sprayed alumina coatings

Self-awareness of Cloud Applications

Cloud applications today deliver an increasingly larger portion of the Information and Communication Technology (ICT) services. To address the scale, growth, and reliability of cloud applications, self-aware management and scheduling are becoming commonplace. How are they used in practice? In this chapter, we propose a conceptual framework for analyzing state-of-the-art self-awareness approaches used in the context of cloud applications. We map important applications corresponding to popular and emerging application domains to this conceptual framework, and compare the practical characteristics, benefits, and drawbacks of self-awareness approaches. Last, we propose a roadmap for addressing open challenges in self-aware cloud and datacenter applications.Comment: Overall: 40 pages, 1 figure, 135 references. Note: This is an extended survey. A much shorter, revised version of this material will be available in print, as part of a Springer book on "Self-Aware Computing". The book is due to appear in 201