Sound absorption and reflection from a resonant metasurface : homogenization model with experimental validation

Efficient manipulation of sound waves by some resonant acoustic metasurface designs has recently been reported in the literature. This paper presents a general theoretical framework for the description of sound wave interaction with the resonant metasurface that is independent of the nature of resonators and the excitation. The equations governing the behaviour of the metasurface are upscaled from the rigorous description of its unit cell using the two scale asymptotic homogenisation. The procedure relies on the existence of the boundary layer confined in the vicinity of the resonators operating in the deep subwavelength regime. The model is capable of describing sound interaction with the array of resonators positioned above or upon the substrate, so that the out of plane direction becomes an additional degree of freedom in the design. It is shown that at the leading order, the behaviour of the resonant surface is described in terms of the effective admittance, whose unconventional properties makes it possible to achieve the total sound absorption at multiple frequencies, broadband absorption, the phase reversal of the reflected wave at resonance and the control of the enclosure modes. The theory is validated by experiments performed in the impedance tube and in the anechoic environment using a surface array of spherical Helmholtz resonators with the extended inner neck. Experimental results confirm the effectiveness and robustness of the resonant surface for control of sound waves

Loss of off-site power transient analysis for a sodium-cooled fast reactor equipped with a gas power conversion system and preliminary optimisation of its operation

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Commande de zones de conflits dans une algèbre de dïode

International audienc

Dealing with Mutual Exclusion Sections in Production Systems : from Shared Resources to Parallel TEG's

This paper deals with the disambiguation of the behaviour of Petri nets including shared resources. In the production management context, they are often used for the modelling of manufacturing cells. But this representation has a poor transposition into dioid algebra.In this article, we design a method to describe such a phenomenon in a dioid of interval. The latter expresses this class of Petri nets models in a formal way. Their input/output behaviours are guaranteed to be greater than the lower bound of the reference model set and lower than the upper bound of this set. In fact, the resource sharing problem is turned into a time uncertainty problem, concerning the access to the shared resource. In this new problem, time uncertainties are bounded and can be described by intervals. Both bounds “confining” the behaviours of the studied production systems in intervals can be manipulated in the scope of the Zmax algebra, even though the original systems are not Zmax linear by essence

Shared resources in production systems: (max,+) analysis

This paper deals with formal modelling of Petri nets including shared resources. These phenomena appear widely in the production management context, for the modelling of manufacturing cells. But, they usually cannot be formally represented in dioid algebraic structures based on sets of scalars. In this paper, we design a method to describe such a phenomenon in a dioid of intervals. In fact, the resource-sharing problem is turned into a time uncertainty problem, regarding the access to the shared resource. In this new problem, time uncertainties are bounded and can be described by intervals. Both bounds of the behaviours of the studied production systems can be manipulated in the scope of the ℤmax dioid, even though the original systems are not ℤmax linear by essence

Modelling Systems with Periodic Routing Functions in dioid Zmin

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Modélisation de systèmes de production à routages périodiques dans le dioïde Zmin

Analyse et Commande des Systèmes à Evénements Discret