Blow up profiles for a quasilinear reaction-diffusion equation with weighted reaction

We perform a thorough study of the blow up profiles associated to the following second order reaction-diffusion equation with non-homogeneous reaction: $$\partial_tu=\partial_{xx}(u^m) + |x|^{\sigma}u^p,$$ in the range of exponents $10$. We classify blow up solutions in self-similar form, that are likely to represent typical blow up patterns for general solutions. We thus show that the non-homogeneous coefficient $|x|^{\sigma}$ has a strong influence on the qualitative aspects related to the finite time blow up. More precisely, for $\sigma\sim0$, blow up profiles have similar behavior to the well-established profiles for the homogeneous case $\sigma=0$, and typically \emph{global blow up} occurs, while for $\sigma>0$ sufficiently large, there exist blow up profiles for which blow up \emph{occurs only at space infinity}, in strong contrast with the homogeneous case. This work is a part of a larger program of understanding the influence of unbounded weights on the blow up behavior for reaction-diffusion equations

Effect of particle shape and fragmentation on the response of particle dampers

A particle damper (PD) is a device that can attenuate mechanical vibrations thanks to the dissipative collisions between grains contained in a cavity attached to the vibrating structure. It has been recently suggested that, under working conditions in which the damping is optimal, the PD has a universal response in the sense that the specific dissipative properties of the grains cease to be important for the design of the device. We present evidence from simulations of PDs containing grains of different sizes, shapes and restitution coefficients, that the universal response is also valid when fragmentation of the grains occurs (generally due to intensive operation of the PD). In contrast, the welding of grains (caused by operation under high temperatures) can take the PD out of the universal response and deteriorate the attenuation. Interestingly, we observed that even at working conditions off the optimal damping, the shape of the grains remains unimportant for the response of the PD.Fil: Sánchez, Martín. Universidad Tecnológica Nacional; ArgentinaFil: Carlevaro, Carlos Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Pugnaloni, Luis Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional; Argentin

Application of Huygens’ Metasurfaces to the Arbitrary Design of a Leaky-Wave Antenna

Leaky-wave antennas are guiding structures that leak power along their length. Their radiation is mainly characterized by the propagation constant (leakage factor and phase constant) of the traveling wave. In this contribution, a leakywave antenna based on parallel-plate waveguide is proposed. Arbitrary control of the leakage factor and the phase constant is achieved by replacing the top plate by an omega-type bianisotropic Huygens’ metasurface, which implements the desired field transformation. The theoretical derivation and design methodology are briefly described. Several designs with different pointing angles (phase constants) and leakage rates have been carried out. Electromagnetic simulation results validate the theoretical derivation, highlight the capabilities of the structure and confirm the flexibility in the design parameters.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Leaky-Wave antennas with arbitrary radiation based on bianisotropic Huygens’ metasurfaces

In this contribution, we present the application of Huygens’ metasurfaces (HMS) to the arbitrary design of leaky-wave antennas (LWAs). These metasurfaces have demonstrated their capabiity to tailor the electromagnetic waves at will. We use them to design LWAs consisting on a parallel-plate waveguide in which the top cover is replaced by a HMS, which implements the desired field transformation. By introducing bianisotropy of the omega type into the metasurface, we have the required degrees of freedom to achieve arbitrary control of the LWA radiation parameters: leakage factor and pointing angle (phase constant). The theoretical derivation of the concept and the design methodology will be described. Moreover, the flexibility in the design will be highlighted with results of two examples of broadside radiation with different directivities.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 706334

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Quinto accésit del Certame

On the use of bianisotropic huygens' metasurfaces to build leaky-wave antennas

The Electromagnetics AcademyHuygens' metasurfaces are considered a powerful tool to achieve anomalous electromagnetic field transformations. They consist of an artifcial surface built of pairs of collocated electric and magetic dipoles that force the boundary conditions for the desired transformation to be ful lled [1]. Despite their possibilities, the achievable transformations must ful l some conditions. In [2] it was shown that Huygens' metasurfaces with passive and lossless particles can achieve an arbitrary field transformation provided that the power is conserved at each point of the metasurface and there is wave impedance matching. However, it was shown in [3], that by introducing bianisotropy of the omega-type, the matching condition can be suppressed, which allows the control of both the transmission and rejection coe cients on the metasurface.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech