Global stability of vortex solutions of the two-dimensional Navier-Stokes equation

Both experimental and numerical studies of fluid motion indicate that initially localized regions of vorticity tend to evolve into isolated vortices and that these vortices then serve as organizing centers for the flow. In this paper we prove that in two dimensions localized regions of vorticity do evolve toward a vortex. More precisely we prove that any solution of the two-dimensional Navier-Stokes equation whose initial vorticity distribution is integrable converges to an explicit self-similar solution called ``Oseen's vortex''. This implies that the Oseen vortices are dynamically stable for all values of the circulation Reynolds number, and our approach also shows that these vortices are the only solutions of the two-dimensional Navier-Stokes equation with a Dirac mass as initial vorticity. Finally, under slightly stronger assumptions on the vorticity distribution, we also give precise estimates on the rate of convergence toward the vortex.Comment: 35 pages, no figur

Renewable beta-elemene based cyclic carbonates for the preparation of oligo(hydroxyurethane)s

Conversion of β-elemene into new β-elemene dicarbonates through epoxidation and halide salt-catalyzed CO2 cycloaddition reactions is reported. Step-growth polyaddition of this dicarbonate to five different, commercial diamines was investigated under neat conditions at 150 °C yielding non-isocyanate-based low molecular weight oligo(hydroxyurethane)s with 1.3≤Mn≤6.3 kDa and 1.3≤Ð≤2.1, and with glass transition temperatures ranging from −59 to 84 °C. The preparation of one selected polyhydroxyurethane material, obtained in the presence of Jeffamine® D-2010 was scaled-up to 43 g. The latter, when combined in a formulation using Irgacure® 2100 and Laromer® LR 9000 allowed the preparation of coatings that were analyzed with several techniques showing the potential of these biobased oligourethanes towards the preparation of commercially relevant materials

A formal model for optimal autonomous task hibernation in constrained embedded systems

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Optimal hibernation policies for energy efficient stateful operation in high-end wireless sensor nodes

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A bird's eye view on reinforcement learning approaches for power management in WSNs

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A Novel Catalytic Route to Polymerizable Bicyclic Cyclic Carbonate Monomers from Carbon Dioxide

A new catalytic route has been developed for the coupling of epoxides and CO(2) affording polymerizable six‐membered bicyclic carbonates. Cyclic epoxides equipped with a β‐positioned OH group can be transformed into structurally diverse bicyclic cyclic carbonates in good yields and with high selectivity. Key to the chemo‐selectivity is the difference between the reactivity of syn‐ and anti‐configured epoxy alcohols, with the latter leading to six‐membered ring carbonate formation in the presence of a binary Al(III) aminotriphenolate complex/DIPEA catalyst. X‐ray analyses show that the conversion of the syn‐configured substrate evolves via a standard double inversion pathway providing a five‐membered carbonate product, whereas the anti‐isomer allows for activation of the oxirane unit of the substrate opposite to the pendent alcohol. The potential use of these bicyclic products is shown in ring‐opening polymerization offering access to rigid polycarbonates with improved thermal resistance

The COMPLEX reference framework for HW/SW co-design and power management supporting platform-based design-space exploration

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Speeding-Up Expensive Evaluations in High-Level Synthesis Using Solution Modeling and Fitness Inheritance

High-Level Synthesis (HLS) is the process of developing digital circuits from behavioral specifications. It involves three interdependent and NP-complete optimization problems: (i) the operation scheduling, (ii) the resource allocation, and (iii) the controller synthesis. Evolutionary Algorithms have been already effectively applied to HLS to find good solution in presence of conflicting design objectives. In this paper, we present an evolutionary approach to HLS that extends previous works in three respects: (i) we exploit the NSGA-II, a multi-objective genetic algorithm, to fully automate the design space exploration without the need of any human intervention, (ii) we replace the expensive evaluation process of candidate solutions with a quite accurate regression model, and (iii) we reduce the number of evaluations with a fitness inheritance scheme. We tested our approach on several benchmark problems. Our results suggest that all the enhancements introduced improve the overall performance of the evolutionary search

A Standardized Morpho-Functional Classification of the Planet’s Humipedons

It was time to take stock. We modified the humipedon classification key published in 2018 to make it easier and more practical. This morpho-functional taxonomy of the topsoil (humipedon) was only available in English; we also translated it into French and Italian. A standardized morphofunctional classification of humipedons (roughly the top 30–40 cm of soil: organic and organomineral surface horizons) would allow for a better understanding of the functioning of the soil ecosystem. This paper provides the founding principles of the classification of humipedon into humus systems and forms. With the recognition of a few diagnostic horizons, all humus systems can be determined. The humus forms that make up these humus systems are revealed by measuring the thicknesses of the diagnostic horizons. In the final part of the article, several figures represent the screenshots of a mobile phone or tablet application that allows for a fast recall of the diagnostic elements of the classification in the field. The article attempts to promote a standardized classification of humipedons for a global and shared management of soil at planet level